> it was probably from using varnish
> straight out of the can (i.e.,over the course of several coats, the brush
> picks up enough dust and particles to start impacting finish). For my next
> boat I plan to pour out as much as I think I'll need into a separate
> container. If a significant amount is left over, it's going through a
> strainer before going back into the can.

I am no expert by any means, and have just finished my first kayak (Patuxent 19.5). To add to this, NEVER use varnish straight from the can. Pour it through a paint filter (medium seems to work well for "captains", or finer) into a clean plastic cup (throw the cup away when your done), then return it through the filter to the can when done. also, seal your can in the mean time. Also, heating varnish to thin it will give thinner, more even coats. Many put the can in hot water, I use a heat lamp. Wipe the work down with pure (not recycled) lacquer thinner, then wait at least an hour before using a tack cloth to wipe any dust away. I have also found that using foam lacquer rollers gives thinner, more even coats then applying with a brush. They will leave bubbles though, so after applying with the roller, tip out and smooth over with a GOOD QUALITY brush. Then repeat from the top until bored.