I removed the channels and worked on my bench carefully scraping the old stuff out with various sizes of flat blade screw drivers, and various small wire brushes for clean up.
Who knows what adhesive may have been used to stick these on (or maybe back on after they have come loose). Pretty much I used solvents mentioned above that I had around. I also had acetone available and used a lot of the adhesive remover Farm & Fleet has in quarts. Use that crap OUTSIDE or under the exhaust fan (I would rather have a bad booze hangover than the pounding head I got from those solvents).
I removed the channels and worked on my bench carefully scraping the old stuff out with various sizes of flat blade screw drivers, and various small wire brushes for clean up.