Using a scraper made a HELL of a difference. Well, once I modified a box cutter blade to fit in it, anyway - The blades that came with the scraper were so soft that the GLUE was pitting them. Ick. Never buy Craftsman razor blades! I used the steamer ahead of the blade to soften up the glue, and then scraped away. Anyway, here it is after a few hours of work.
It's about 98% done. I've still gotta get into the corners and take off the tiny bits that I missed like this:
Of course, I was greeted by this when I got home from work that night:
Looks like it's time for new wheels and tires!