Best way to remove barrier coat
It sounds from your message like you are taking on this task yourself.
Probably what I will do when the time comes is try chemical strippers to see how well they can take off some or most of the existing coatings. Hopefully, what''s left can be carefully sanded off. You can rent a vacuum sander from a rental place (house painters use them on big jobs, I guess), but they don''t have the ability to take off a lot of material quickly like a high speed disc sander. Plus they are somewhat unwieldy (they have a power head attachment and a vacuum hose to heft) so your arms will tire after a while. Hopefully, most of the spots on the hull will require a light sanding with the vacuum sander; for stubborn spots you can do it with a disk sander (be sure to wear a good respirator), make sure you''ve got a drop cloth to catch the toxic dust. You''re right, it''s going to be a daunting task, I''ve never done it but I can tell just from how much work it was to do a "quickie" sanding and repainting job last spring on the trailer.