Originally Posted by CajunCJ
I found a grinder with a wire wheel worked the best for me and yes it's going to be a lot of work. Good luck
I've installed several bed liners in both truck beds and in Jeep tubs. Once I got a speck of bedliner on the outside of the bed. I called the manufacturer of the brand of bedliner I was using. They said that stuff is designed to not come off. They also said they didn't know of any chemical that would remove it. I used SEM brand bedliner, SEM Products - Catalog
I've also patched several bedliners. I know a friend that works in a body shop, and I patched a couple of bedliners on trucks that were fixed in his shop. Anyway, the only way I've found to remove the stuff is to take a wire wheel on a grinder or something similar to remove it. Of course this takes the paint off. If you want to have the liner on, you need to prep it correctly, and this means make sure you rough up what's going to be under it, whether that's bare metal or scuffed up paint. If you just apply it to the existing paint, without roughing it, it has nothing to stick to. That's why the PO's job is failing.