I used the polyC method last year on my pusher CF-188. I had to seal the balsa surfaces first against the water based polyC. It took several coats to fill at least 6. It is best use talcum. I used 75 oz. cloth. I generally found the surface wasn't very hard and is easily dented. I haven't tried an epoxy method yet, but one of the other club members swears by the West System.
I did find that the polyC had enough of an odour to not want to apply this in the house in the winter months.
Jim
ORIGINAL: RCdude13
Polycrylic is the way to go. It has no smell so it can be done in the middle of winter in the basement. It is a lot lighter than epoxy or fiberglass resin because most of the water evoporates. Yes, you do have to seal the wood before you start. You only need one coat of Polycrylic to attach the material however (I use dress lining from Walmart). The second, and if needed, third coat is a thick mix of the Polycrylic and talcum powder. This fills in the weave of the dress lining completely, and is very easy to sand. Once sanded, the surface is ready for panel lines, rivets, and any other surface details. My last warbird was painted with Benjamin Moore exterior latex...I'll never use anything else. The only drawback to this system is it is prone to showing hanger rash, but my theory is that I build them light so they fly well and then transport them with a little more care. My Ziroli Hellcat came in at 33 pounds with no lead needed for balancing.