my opinion
the boys are right, always wet,
only use dry on jell coat on boats (learnt that when i was working in a boatyard repairing sailing singhies) (i was desperate! working with gel coat is awful)
i wet and dried my hole boot lid, its good, id start with 600 maybe? depending how rough, then move onto more fine stuff to get it flat
keep it was as you can
then moving onto the finer stuff, if all you own is 600, then fold it onto itself and rub it against itself (sands it self to a less abrasive state) sometimes needs must you know
