My brother is at the "nearly finished" stage of building a Flower Corvette. The Revel plastic kit, not the new version. He has just finished painting the boat and is about to put Transfers on, etc. He has used Halfords spray paints fo the model and has a can of their Matt Clear Varnish to put onlast, He sails at a water that has slightly brachish water, he is wondering, will this affect the finish, does he even need the varnish? Your advice would be appreciated, He knows about rinseing off the model in clear water after a sailing session.