Give them a slight rub down with 1500 wet n dry.

Smooth.

Painted them black. However Ive managed to get some runs on one of the lights

How long should I leave this before sanding the runs out?

Also why does the paint seem to be going on sort of dusty. Its flat in some areas and very shiney but in others it feels a tad sort of dusty???

All in all I suppose they will look ok once smoothed out with some more 1500.