@kjhambrick --
After lightly sanding the body tube to remove the glassiene finish (cardboard tube), I used Krylon gray filler primer to fill spirals, as well as any dings that occured during construction. After it dried, I sanded the filler until the only gray that remaind were small spots and spirals that were filled. If you leave more filler than this, you're just adding weight.
If you still have spirals and/or dings, apply another coat, then sand again. On my rocket, two coats of gray filler were sufficient to fill spirals and dings.
Next, I sprayed Krylon white sandable primer. This is the primer for top-coat bonding, not filler primer. I sanded the white primer with 400 grit, then 600.
Then I applied the top coats with Krylon Fusion.
Note: I didn't sand the top coats at all. Just the primer.
The entire rocket was then coated with Pledge Revive It acrylic floor gloss, using a foam paint brush.
Honestly, that finish comes from the floor gloss, not from sanding. Get your last coat of primer smooth—like 600 grit smooth—and let the top-coat paint do its thing. I sprayed 10 to 12 inches away from the rocket, three very light coats 10 minutes apart. Then I let it cure for two weeks before applying the floor gloss.
Different finishes do affect rocket performance in terms of velocity and altitude. In OpenRocket, double click a component—nose cone, for example—to open the dialog window. You'll see a Component Finsh popup button (lower right in the image below) where you can select from a number of finishes. You can click the 'set for all' button if the entire rocket will have the same finish.
The finish on my rocket was modeled as 'Smooth'.
OpenRocket's ability to accurately simulate velocity and altitude is almost entirely dependant upon entering accurate weights and measures of every item that goes into the rocket. At the very least, weigh the finished rocket with everything—parachute, altimeters, etc.—but NOT with a motor. (OR knows the weight of the motor you've selected for the simulation, and will do its calculations with that weight figured in.) Then enter that weight as an override in 'Stage'.
This is the data from an OR simulation on a G74-9 motor:
Apogee: 1616 feet
Max Speed 296 mph
Time to Apogee: 9.45 secs
Total Flight Time: 166 secs
Average Descent: 9.5 fps
This is data from the actual flight as recorded by a FlightSketch Mini altimeter:
Apogee: 1559 feet
Max Speed 303 mph
Time to Apogee: 10.2 secs
Total Flight Time: 165.4 secs
Average Descent: 10 fps
In my book, that's close enough.
I hope this helps!
