||I did decide to try to get the hatch as clean as I can. A heat gun did a great job softening up the foam/adhesive, then I used a plastic scraper (HF trim/molding tool) to get the heavy layer off.
I then applied some Goo Gone and let it work for 5-10 minutes - made a big difference. Some would come off with a rag, but most of it took some scraping with the fingernail. It's still tedious and time-consuming, but it didn't take a lot of physical effort. Once I have everything removed, I'll use the Bullfrog stuff for the rest of the rust. Hope that works as advertised - like I said, highly recommended by my uncle who has had a LOT of clocks to clean up following the Houston flood last year.
I'll let you know how it goes.