Homebrew PCBs

Has anyone tried using any of the various spray varnish products as a solder mask? More often I'm finding the need to mask areas when soldering tiny parts, the current dilemma being the area around the thermal pad on a HTSSOP package. I've been using kapton tape but there are times when it would be much easier to tape off the pads and spray a whole section. I've seen solder mask touchup pens but they strike me as very expensive considering the tiny amount they contain. I thought about thinning some epoxy resin and painting the area with that. Curious what other ideas people have or what has worked for you.