You'll get a thousand different replies on this. You can search TRF, but the easy answer I have is:

Elmer's Fill-n-finish (available at Lowes) thinned with water. Brush on both sides of the fin (before attaching to rocket) and clamp with wax paper and weights to prevent warping. Sand, then prime either with Kilz or an auto-body high-fill primer. Wet sand to your heart's content.

My L1 rocket took 3 cans of Kilz (overkilz?) with most of it getting sanded off. For small body tube spirals, Kilz alone without the FnF works well.

Try a few different methods and see what works for you. I'm still playing around.

-Ken

what's trf?

I use the body putty glaze filler. Comes in a small tube, it's easy to work with and sands easily. It's great for wood fins.

Ken.

I found some filler at Hobbytown that is really good stuff. A bit expensive but well worth it. I seem to recal is was 7 ot 8 bucks a jar. I like it a lot better that Elmers. It is very smooth and dries quickly.

For the small fills, a few good coats of Kilz work like a charm.

what's trf?

The Rocketry Forum. http://www.rocketryforum.com/

From my view, it's the online forum with the most traffic, more so than rocketry online.

Lots of good info and decent folks.

-Ken

I found some filler at Hobbytown that is really good stuff. A bit expensive but well worth it. I seem to recal is was 7 ot 8 bucks a jar. I like it a lot better that Elmers. It is very smooth and dries quickly.

For the small fills, a few good coats of Kilz work like a charm.

hmm, i just went and bought the elmers last night ... i like the price, ~$1.50/small tub! however, if this hobbytown stuff is that much better ... well, should i switch? what's wrong with the elmers, especially if i water it down to make application easier?

For balsa fins Elmer's and sandable primer work great. No need to spend the extra dollars.

But for those odd occaisions when you need a little more, I like that Hobbytown stuff. It has the consistancy of spreadable margarine. For bigger birds I use bondo and then cover with sandable primer. I wish I could learn the right way to mix small batches of bondo as I always seem to make it cure either too slow or too fast.

so for the little stuff (ie, estes rockets), you think the elmers will be fine for filling in balsa fins, and those annoying spirals on the tubes? thanks for all the input!