This is a regular maintenance task necessary to keep your compressor working efficiently and preventing overheat auto-reset of the compressor. There is not magic spray, or short cuts. Find an appropriately sized and shaped brush attachment for you boat's vacuum system (you have one right?
). I do this job in the spring when I have my mini shop vac aboard for bilge clean up. Carefully brush the fins in the direction they are oriented and wiggle the bristles into the condenser core. Do the same with the compressor board and heat sink. On my boat I have to remove a duct to get at the condenser fins. Bit of a job, but necessary.