Runs on paint is a bore, and I am painting a Ford KA tomorrow, so I will be careful, but the guy who taught me to spray always carried a clean 1/2 brush in his top pocket, and would brush the runs away, just to get rid of the bulk and speed the through drying of the paint so it could be flatted quicker. This avoids the sinking feeling in the pit of the stomach when one realises that the run you have just attacked with the wet and dry is now a smear of semi solid paint, and you have pulled it back to the primer! start again time!! Luckily the KA is basecoat and lacquer, so build up solid colour, then lacquer it all to a finish! This job has reminded me why I gave up car repairs in about 1982!