Paint for foils

I'm reviving a couple of older boards for older boats. One of them has a fiberglass repair. I'll be using I'm thinking about spray primer and spray enamel appliance paint and some sanding on the areas where the white surface is worn off. How effective will that be?

That's about the best you can do from a rattle can (search on Krylon in this forum for more info)
Works well on rudders, on daggerboards, it will wear off in places from the up/down movement in the trunk.

IMHO, a well sanded board, wiped clean of any contaminant doesn't require primer. It just doubles the time and cost

I use 'plastikote', an automotive spray formulated for plastics.
Thorough prep - cleaning, filling, rubbing back, wet sanding with mid range grits and clean with thinners - is my primer.
Gentle wet sanding with v.fine grits to finish after spray...perfecto