I have used the Balsarite made for coverings like Monokote for years and have experienced no difficulty at all with the product. Would not cover a plane without it. Here's what I do: Be sure you use the film formula Balsarite; the green striped can (COVR2515). I brush a coat straight from the can (not thinned) via a throw-a-way foam brush over all the surfaces, both balsa and plywood. After the Balsarite dries ( I usually wait overnight) I then go over the entire framework, lightly sanding to knock down the surface a bit, with 320 sandpaper. Vacuum the entire framework and then I go over the wood with a paper towel to pick up any further dust. Now, I then use a large T-pin and holding it so just the point extends past my fingers I proceed to poke tiny air escape holes in the framework. You don't need to go through the wood just provide some relief for the air to escape under the covering. Do this for both balsa and ply and have about 3-4 pin-holes per square inch. Yes it takes a bit of time to prepare the surface as I do but the covering has always gone on and stayed put using this method. When I iron down the covering it comes out very smooth and you do not see any of the prep work showing through. Try this method out and see what you think as your covering material continues to look great after time. BTW: Use a covering sock when putting the Monokote down and you'll like the results. Also: I do not use the Balsarite as a sealer on the firewall area of my models; I use 30 min. Epoxy instead. Mix a sufficient amount on a piece of paper and heat via your Heat Gun just until the Epoxy starts to spread like water. Brush this mixture onto the firewall via a foam brush and let dry. You'll be surprised at how easy it is the "paint" the heat thinned Epoxy on the surface. You have to work a bit faster with the Epoxy as the extra heat will activate the Epoxy faster. Hope this helps.

Joe