Now for covering, which I'm sure everybody already knows how to do but I'll go through it in case someone new comes across the thread.
For brushing, I am using 60-40 mix of 60% thinner. I start by brushing nitrate dope on the balsa everywhere that the covering will touch (remembering that it will shrink and create concave curves). I could use butyrate for the entire project but it will shrink enough to warp the wing. So I'll start with nitrate and switch to butyrate for the final coats when filling the weave. Two coats, with the second going on after the first is dry to the touch. This time, instead of one more coat, sanding, and a final coat of nitrate, I put on two coats of sanding sealer and then sanded. Next time I'll thin the sanding sealer even more, 2;1 or 3:1. There should be enough coats that the wood takes on a sheen. This is important because uncoated balsa sucks up the dope and can cause problem spots when you try to fill the weave. Another thing to note is that the dope melts the fillers, so be careful about repeatedly brushing over the filler. Just get it on, quickly smooth out the brush marks and leave it alone. The Super Fil, however, does not melt and that's why I switched to using it for the fillets.
Then we cut out a sheet of silkspan for the bottom of the wing. The silkspan goes on, smooth side out with the grain running along the longest dimension (i.e. wing spar). The medium grade Brodak silkspan I used before was rather heavy and I finally got some gas model grade from Sig which is much lighter. So this time I'm going with the Sig brand.
I sprayed the tissue down with water, placed it over the wing bottom, and teased out the wrinkles. Whenever the tissue starts to dry out, I wet it down again. Using the nitrate dope, I rub the dope into the tissue along the trailing edge, just on the perimeter. After rubbing it in a bit, it starts to feel gummy and the tissue adheres. Working from the trailing edge to the leading edge to the wingtips, I glue down the tissue, using a single sheet for the bottom. It may be easier to use a separate piece of tissue for each wing tip, but the curve here is easy enough to do it all in one go.
At the tips, I rub the dope in perpendicular to the edge of the wingtip, pulling the tissue down taut. By working back and forth along the wing tips, and reapplying more dope to detach and reglue the tissue, I can work out all the wrinkles (who needs heat shrink). I then do this along the entire perimeter, laying down a second coat.
After two coats along the perimeter, I use light sandpaper to trim the tissue and then tack down the fuzzies with dope. The sandpaper feathers the edge and allows the seam to easily disappear, while making a very clean and close cut. Just need to be careful not to cut through any underlying tissue. Then I flip the wing and cover the top in the same manner as before.
Once the wing has been covered, I go back and put on three more coats on the perimeter. This is important because dope melts dope. When I start filling in the weave of the tissue, I do not want to melt the dope on the perimeter and have the tissue draw back (particularly when I start tautening).
I gave it a final spray down with water and hung to dry. I'll do the same for the control surfaces, fuselage, hatch, servo horns, and the landing gear panels.