Skipping the filler/primer step: crazy?

Up until now I've followed pretty much the same finishing process on all my models:

1) Fill and prepare all surfaces. Fins are almost always papered, other balsa pieces are CAed or papered or CWFed or some combination, spirals are filled with CWF and sanded.
2) One heavy coat of filler/primer (I've used both Rusto 2x and Duplicolor with approximately equal results)
3) Let dry
4) Sand most of it off
5) Paint top coats (usually Rusto 2x), two light coats and one heavy coat in a session.

Frequently, I find myself needing to sand and in some cases put second finishing coat on at the end, despite starting with a very smooth surface in step 4. This is generally a result of my lack of skill in painting, combined with haste because I'm usually working within a narrow time window. I've actually been thinking of trying a slightly modified version of step four, which is to paint a couple of light coats, let dry, sand, and then apply one final top coat. Whenever I've applied my final top coat on top of a sanded-smooth surface I've gotten very good results.

Anyway, despite my success thus far, I'm having a bit of a thought experiment on what would happen if I skipped the filler/primer step, and instead simply shot a good coat of regular primer immediately (in the same paint session) before applying my first top coats. I have two reasons for considering this:
1) Eliminate one complete paint/dry cycle. For me, finding opportunities to spray is incredibly difficult, so anything I can do to reduce the need is extremely beneficial.
2) Eliminate the filler/primer sanding step. Not because I hate doing it, but because on intricate LPR models I'm finding it to be incredibly difficult. Priming all the parts beforehand works sometimes, keeping the primer off the future glue joints is not always straightforward. Trying to sand the primer off an intricate model after assembly in some cases almost impossible.

So exactly what sort of downsides am I likely to experience if I do this? I know that there is a certain amount of surface irregularity that I will no longer be eliminating if I skip the filler/primer, but I have no idea how bad it would be or where exactly the most likely trouble spots are. I should say going in that my objective for my paint jobs is "very good" but not "perfect"; I always end up with plenty of imperfections even with using the filler/primer, but the results are still pretty nice.

All input welcome.

I usually do the filler and 3 or 4 layers of high build primer with sanding in between. If you are trying to fill the spirals with just the primer, it will take many, many coats of even the highest build primer. If you do not want to see the spirals, I would stay with the filler.

Rough surfaces have more drag but unless you are doing competition I don't think that matters. In the end it is all personal preference.

I am not big on finishing and generally get them looking good at 10'. I generally only fill spirals on an occasional model of if I have a non-rocket tube with really deep ones. However, painting over unprepped balsa leaves too bad a finish for me. So, I do a coat of Fill'n'Finish or paper them. I almost always prime because I find too many colors have a different tone over different color surfaces. It also shows off where I did an exceptionally bad job filling or have some other surface imperfection.

I think you're going to get a mixed bag of answers on this question. Since I'm not as anal about getting a museum quality finish, I give the raw rocket a regular primer. Then buff with a 00 or 000 fine steel wool. This alone will smooth out the primer and it'll get shiny. Rough areas can be lightly sanded afterward. Wipe the dust and steel fibers away and be anal about doing that. Then go with a flat white undercoat. This is especially good if you are going to use med - light colors. Then I start using the 2X to paint. Your preferred tube prep can precede all of this also.

I'm pretty serious about the finish on all my Rockets.

That being said I have Not used as single "Filler" material in over 20 years.
I discovered the "Cheapy Primer 3 coat method in the late 1990's. Currently I'm using Wal-Mart Color Place grey, brown and black sandable auto primer.
I usually purchase in 2 or 3 Case lots. 12 to 18 cans to get the price down to around .88 to .97/ 12oz rattle can.

The Procedure is very simple. Build your model. dry sand all balsa parts with 400grit sandpaper just to semi-smooth the sapwood. If the Balsa has very deep grain I'll paper towel swab a coat of medium CA or MinWax wood hardner to seal the balsa. If the balsa parts or basswood have the normal depth grain the Sealing coat is not needed. Wipe down the entire model with a tac-rag. 3 heavy wet coats of Cheapy Primer are applied to the entire model allowing 3-5 minutes between coats to tac. After all 3 heavy wet coats are applied the models is set aside to dry overnight or in humid weather until the "Sniff Test" tells me the primer is ready for sanding. Sand with 220 or 240 grit dry sandpaper until the model is completely smooth without body seam or wood grain. If we hit bare wood or cardboard apply another 3-coats of cheapy primer, Allow to cure then sand with 320-360 grit sandpaper until we have as smooth a finish as is possible. Once satisfied with the smoothness and lack of blemish, dog hair, dust particles or tiny bugs apply a base gloss color coat (Generally a light color unless the model is to be matallic in which case the base coat should be Black.)
don't bother sanding primer beyond 360 grit. we Want to leave a bit of "Tooth" those sanding Peaks and Valley to help the paint adhere to the primer.
WARINING: Do NOT Wet or Damp sand primers on Wood or Cardboard parts or tubes. Primers are porous by chemistry, they will wick moisture all the way to the wood or cardboard causing warps and/or delamination. (DRY SAND PRIMER ONLY) Save the wet sanding to the finial gloss color top coat.

Regardless of Rocket size I usually get 1 or two Standard and MPR size models from a single 12oz can. I've primed as many as a dozen Micro models from the same primer can.
I used to pay the extra money for high build primers but have been pleasently surprised at the amount saved by using the "CHEAPEST sandable primer" I can get my hands on.

Since perfecting this finishing technique I can't recall the last time I used a Brush-on or spread on filler of any kind. A few finished examples below.

Rocket only looks good for the first flight anyway....

What?? Are you nuts? That's part of the secret initiation rights for steely-eyed rocket men! Blasphemy! Baliff-wack his...rocket!

Bat-mite said:

Rocket only looks good for the first flight anyway....

Click to expand...

Not really: If you've done a proper job your rockets can look good for more than a dozen flights. Seriously; I have many rockets that have more then 15-20 flights that look almost as good as their very first flight. Sometimes it's only a matter of a good coat of Wax that keeps them looking as good on the pad as they do under the prep tent.