I am starting a company making longboards and figuring out best mfg processes. There is a closed cell polyurethane foam core with cast urethane bumpers surrounding the entire rail (edges/sides). I wish to have a carbon top and bottom, both with a glossy finish. Sides will be cnc machined so no carbon will touch in the final project, however it is fine if it does still. Ideally I want production times at an absolute peak, so infusing both the top and bottom layer in one operation would be ideal. I would be okay with clearcoat sprayed for a glossy finish if that works, however one operation is of upmost importance.

Any tips or pointers for this?

Double sided finish in one shot really means you need to be working with compression rather than vacuum, which means either RTM or pre-preg. Very very difficult to do with infusion, as you need precisely matched tooling and a medium for the resin to flow through. So it can be done with infusion if you have matched tooling that applies appropriate consolidation to both sides of the laminate, and a core material that facilitates resin flow so that you dont need the flow mesh on the B-Side that would ruin the finish you're after. 

Easier to do with pre-preg. Workout your consolidated laminate thickness, machine a mould that will allow that exact thickness when the mould halves are bolted together, then just lay it all up and throw it in the oven. No need to worry about getting resin to flow through it, and once you've got the process sussed it will be very very consistent.