While I haven't tried the WB Poly method I have used both Epoxy and Polyester resins. If applied correctly there is very little weight gain to the over all finish. The best method I have found for applying the resin is using a small roller. The its simplay like painting your wall. There is no need to scrape off the excess because there isn't any. Two coats and your good to go.

Tom Pierce's use of WB poly works but to me it doesn't sound like much less work if you have to seal the balsa and then sand and then apply 4 or more coats to get a proper surface.

But there are many ways to accomplish the same result in a finish. As to what's best is oft a matter of opinion