There’s almost always a little dust that settles onto the last coat of finish before it dries, even when you spray fast-drying lacquer. With slow drying varnish, there’s always dust stuck to the finish.
As long as the dust isn’t excessive and as long as the particles aren’t large, you can make the surface feel smooth by rubbing with a brown paper bag. Give the finish a couple of days to cure so you don’t scratch it.
A smooth feel is critical when judging the quality of a finish. It’s natural for people to run their hand over a finish. Feeling dust nibs says, “This is not a great finish.”
You’ll be amazed at how well the brown paper bag trick works. It doesn’t remove the dust; it just levels it so you don’t feel the tiny bumps anymore.