I do a similar thing with compressed air, on both varnish and
polyurethane. I have used polyurethane on scorched wood in a thin
layer, blow off with air to remove excess. After first coat I do fine
sanding and re-apply thinned urethane for ultra thin topcoat, leaves a
nice finish. Haven't used oil in a long time, as it leaves a bit of a
'tooth' on the surface that is hard to dust, and it also makes wood,
especially walnut and curly grain, too dark for my taste, hides the
grain, color and variety...