I changed the oil in the rear differential and was scraping off the old RTV. Once I got the big chunks off with a razor blade scraper I used on of those grey paint remover pads from 3M (they look like the green scouring pads for pots but much more coarse) to get the rest of the RTV off. It worked great and fast.
BTW, I experimented with using just a gasket coated both sides with grease instead of RTV. So far, since last Saturday, no leaks and I did a two hour, 70mph run down the Interstate since then.
Got the gasket/grease tip from another poster here a few weeks ago.
Fire Cracker Red