
Originally Posted by
Simon Barden
Never sand back too soon when you have got a run. Let the finish dry for a couple of days. Thicker paint means that the inside bits of the run are still wet when the surface feels dry. The solvent in the paint/lacquer will soften the layers underneath, so when you sand through the hard skin, the sandpaper catches the softer paint underneath it and drags it out, leaving a pit in the finish. So just give it time.
I find it's easiest to apply all the coats of one colour (as you are almost bound to get at least one small run with each coat), then wait for that to fully harden before sanding down all the runs together. Any sign of the paint/lacquer still wet underneath the thick run areas and just immediately stop and wait for another day or so.