Here I'm cleaning up the case (again). A combination of acetone and mechanical scraping seemed to yield the best results (though I don't think there's any getting around this job being a PITA). The acetone did best where the sealant was still clearly uncured. I tried to carefully use a razor blade in a few spots, which worked well, but I noticed that it was too easy for me to potentially scratch the case, so I stuck to plastic scrapers.
I will say that the big globs of squeezed-out sealant that I had on the inside of the case were NOT easy to remove. It's hard for me to imagine those things somehow coming loose and then interfering with the oil system... but, still better to have none at all!
Jake