I bought 15 Diamond Chase frames (25x36) a while ago for very cheap money, but they were covered in dried ink, plastisol, tape fragments, glue, etc.
I didn't want to use solvents, etc., to clean them before I reused them so I did something different. Ran the tubes under running water, used razor blades to get most of the tape pieces off, and Brillo pads to remove the rest. Works great. Took about 30-45 minutes to do 1 frame (4 tubes and the brackets). A bit of a hassle, but I completely avoided using and breathing in any solvents. The tubes are mirror bright and very smooth. See photos.