very very fine wet and dry and just rub the run then polish it up so it kinda blends in, im trying to remember if we used do it that way in the spreyshop, sounds about right tho good luck m8
Sand it down till it's smooth then respray or you could try this
(this may sound strange) get a heat gun on it till returns to it's shiney state!
This has worked for me but only a few times