I apply varnish with a 4" foam mini roller, up and down, then side to side to get a nice even coat. Then tip with a foam brush from dry to wet. Work in 2 to 3' sections down one side of the boat and back the other. Work at a good pace and do the tipping before the previous 2-3' start to dry. There will be a little overlap in the center, but that's the scratch zone anyway. Focus on the sides of the canoe, what you'll see when it's on the water, the bottom will take care of itself. The roller and tipping brush will be spent after applying one coat on a hull, so don't bother trying to clean them.
You should be able to get 3 coats on the outside of an average sized canoe with one quart assuming you don't go too heavy, which you shouldn't to avoid runs and sagging. I have used a brush and feel that it is more difficult to get an even coat. One strategy for best results is to do the first two coats with one can, then do the final exterior coat with a new can. A new can of varnish is much nicer to work with that the dregs. The remaining varnish is for the inside.
Spar varnish from different manufacturers is different, with different recommendations. In general I only thin the first layer if I'm applying to raw wood, or if the varnish seems a little thick and never for a final coat. I use McCloskeys and have never felt the need to thin when applying to a hull.
Mark
