I would go with this, 2 gal's should work. Just brush on and hose off.........
is a brushable water-based paint and plasticoat remover that is biodegradable, non-toxic, user-friendly and environmentally safe. It is made in Australia and difficult to find, but worth it.
RemovALL™ 220 is
effective in removing tough industrial coatings like epoxies and urethanes from non-porous surfaces like metal, concrete, masonry and brick. We sell it because vintage Airstream owners have found it to be the best product for removing plasticoat from their trailers before polishing.