If you put CA on it, you will most likely need to sand it. Thin CA leaves a crusty residue and also swells the wood slightly. Depending upon how much you put on it, you might not get enough swelling to worry about, but you will definitely need to smooth it out. Give the CA plenty of time to fully cure before you start sanding it. Thin CA, when applied as a thin film, bonds and cures almost instantly, but that is not what you will be doing here. You will be applying a much thicker coating than that, most of which will be in, rather than on, the wood. Thicker layers of CA take a long time to fully cure, so give it at least overnight. As for sanding, use a medium to fine grit (like 220) and use gentle, light strokes. Don't bear down too much as you sand; let the sandpaper do the work. Stop frequently and check your progress. Concentrate on removing the crust and getting down to the bare wood, or most of the way down to it, anyway. Do not try to sand out pits, holes or depressions in the wood itself; that is what filler is for.
Especially for nose cones, I often use a thin sanding sponge pad instead of sandpaper. I especially like the line of sanding sponges that Norton makes. These aren't the brick-like or block-like sponges, but are the thin pads. The Norton pads are the ones that are in the garish bright colors: blue red and yellow, depending on the grade. Note that the red sponges are in two different grades, "100" and "150." I mostly use the red "150" pad and the yellow "220" pad. The yellow pad is really better for sanding primer, though. These thin pads conform to the shape of the cone much better than any paper-backed sanding medium does, and so they are much less likely to mess it up.
Personally, I don't care for treating wood with CA, because the sanding afterward can be a real bear, and it can distort the shape due to swelling. A good sanding sealer will provide pretty much the same level of protection, and it will be much easier to work with. I like to use Delta Ceramcoat All Purpose Sealer on smaller balsa nose cones, but for the Iris I might prefer to go with the more expensive but superior Pine-Pro Sanding Sealer. You can find the Delta product in the crafts section of Walmart; it will be in with the tole paints. Pine-Pro Sanding Sealer can be found at hobby stores, in or near the pinewood car section.
There are other options for strengthening and finishing your nose cone, too, but some of them are a bit more involved. One fairly simple technique is to just coat it evenly with wood glue or even white glue. You can put some of either one into a dish and thin it slightly with water so that you can apply it with a brush.
More involved techniques include treating the nose cone with Minwax Wood Hardener or coating it with laminating (or "finish cure") epoxy resin and sanding it smooth. In any event you will need to sand the surface of the cone to give it a smooth finish so learning how to sand non-destructively is a skill that you will need to develop.
You must also accept the fact that you will always need to handle the Iris nose cone with some care; that's just the reality. Give it extra padding when you are transporting it to and from a launch, and mount the rocket somewhere that is up and out of the way when you have it at home. Mount it in such a way that it will not topple over and that nothing will topple into it. And remember, in the event of disaster you can always just buy a replacement nose cone from Semroc.
