For flat (no sheen, not shiny) surfaces you'll want to go with our standard Multi-Surface Paint Touch Up. It was predominantly designed for walls/trim/cabinets/etc., but is very durable and should work for you. If you want a sheen or for an added layer of durability and protection, we also offer Clear Touch Up in a range of sheens, for all your needs.
For high-gloss (high sheen, very shiny) surfaces you'll want to go with our Appliance + Porcelain Paint Touch Up. These work best on the outer surfaces. If it's going to be under water, make sure it is fully cured (dried) before being submerged (for more information on high-moisture or underwater usage, see here).
