I too use this method. I do give the balsa a coat of sanding sealer and a final 320-400 grit sanding before glassing. I place the glass on the surface (.5 -.75 oz), brush it with a drafting brush, then apply the epoxy with a small disposable brush working in 1 oz batches. Once the epoxy is applied, I use a small squeegee (phony credit cards work well) and squeegee off the excess epoxy. I then use a roll of toilet paper to blot off that last little bit (some don't think this is necessary, but it's cheap and easy). Once cured, I use a high build auto primer in a rattle can. I apply a coat, let dry and wet sand most of it off with 320-400 grit. Rinse and repeat as needed to fill the weave. For small dings, I use auto spot putty, for larger dips an low spots, I use epoxy/microballoons. I prefer the redish phenolic microballoons. They're lighter and easier to sand than the white glass microballoons.

Scott