I got a carbon fibre numberboard that was in a bit of a state, originally I had planned on using it just as a template, but I think it could be saved.

I was able to remove the outer layer of clearcoat, which seemed to have been applied by a spoon it was so thick.

I've rubbed down the second coat of clear, using 1200 wet and dry, and its now smooth and shiney except for a few places, where the first layer of clear is rubbed right down, almost to the fibre.

When its wet, it all looks shiney and glass like.

When its dried off, and cleaned with alchohol, there's a few matte patches.

If I clearcoat, and wet and dry, and repeat this a couple of times, will I get a good finish across the board?

Or should I continue to wet and dry down until the whole board is matte, before I start spraying?

You should flat it off without going into the fibres and then clear coat it with 2K.
The resin used in carbon layup is basically the same stuff 2K paint is made from.