To completely refinish them I use gelcoat and spray it and wetsand it. It comes out impeccable. If you're not realy proficent in gelcoat repair, I'd stick to either just wetsanding or using an epoxy paint and then wetsanding.
I'm not sure about the legality of using an epoxy paint... but it looks really really close to the original finish and should be fine for club racing.
Some people suggest painting with a slightly different color so fairness can be seen when sanding. If only slight scratches there are probably two approaches. One is to use an epoxy paint that will resist scratches (but is very hard to sand to a smooth finish)
The other approach is two-fold. First use an acrylic spray can that can be easily re-applied to patch scratches quickly (week to week if necessary) and second, check the centreboard trunk -it may be causing the scratches.
I sail a lot on a lake where the beach has granite sand that really scratces if it somehow gets in the trunk and there is weed that somehow attracts grit and scratches the board each time you raise it for a reach.
Overall the acrylic spray can seems the best compromise because I can rub out scratches using auto cutting compound or brasso (metal polish) between races if necessary and when needed (cover coat gets too thin) I can patch the board during the week with a quick spray and then wet and dry followed by cutting compound buffing the next day.
The 3M tapes used by the Musto Performance Skiff to line the centre case may be a better solution but seem to be illegal at present for Lasers.