Went over with a razor blade by hand to pick off a few spots of gasket material, followed with Scotchbrite using some brake cleaner to degrease.
Finished chasing the other 9 bolt holes, I hadn't done a couple. Just wanted to make sure before I went too much further, ya know.
Anyway, I think it's mostly corrosion at this point. The HG came off in one piece so that was actually not too bad. I might try to find that cup tool. I do have a small Scotchbrite wheel for a die grinder I think around here.
I'm using a factory HG so I'd guess the high and low spots should match up. Not really feeling any spots catch a fingernail, so good, bad or indifferent?
The old timing cover gaskets are still being a pain. Hardened and torn. So I may have to get tougher on them but I'm not worried there as those are thick enough fiber and get a light smear of RTV. Might take a wire brush or something like that.