What adhesive should I use on the rear panels?
 

Someone used a bad adhesive to attach the vinyl on the rear panels a couple of years ago. It's all coming apart and I want to adhere it so it stays put. Spray contact adhesive or any other suggestions?

3M spray adhesive in the spray can always worked well for me, not too little, not too much ,on each surface and let it tack-up, Then make sure you get it right the first time. Most important is that surfaces are clean. Most common reason for failure are dirty surfaces, for rubber trim 3M weather strip adhesive, I think thats what they call it, its in a tube like toothpaste, its black, make sure you get it right the first time because you will likely tear the rubber if you try to take it off, and it doesn't clean up easy. IMO

There are different grades of 3M spray adhesive. Get the best they have, 3M Super Spray Adhesive. I used the regular stuff once and it didn't hold in hot weather.

The panels and vinyl have all the old adhesive, what ever kind it was. What a mess. After I removed the vinyl I couldn't easily remove the adhesive so I went to the sandblast shop and removed it all that way. I bought some 3M Rubber and Vinyl 80 Spray Adhesive.
Any thoughts on how I can get the adhesive off from the vinyl?

A bit labor/time intensive but you might try laying the vinyl side down on a hard flat surface and see if a lot of it will "roll" or rub off with your hands. If it's still pliable and rubbery some may come off using this method. Then you could try a white or grey scotchbrite pad but pay attention if it's pulling the adhesive off and don't over-rub the "clean" areas (that should be a vinyl with a white sort of backing material on it).