MEDIA BLASTING!!! That is the way to do it if you have the extra money. It is worth it in time spent...
As for what I did, I took a DA sander to most of mine with 80 grit to remove everything that could be reached. Then I used a drill mounted scotch brite pad (you get them from eastwood, and I think they are called a stripdisk). I used a small cheap air drill so I could get it into tight places, and also to throw it away once the bearings were shot from all the side loads I had put on it. Then I took a gasket scraper and picked out the tough areas... from there it was all by hand... mostly with 180 and it came off fairly easily. The DA probably got 90 percent of it, though you tend to rip up the paper on all the little metal snags, etc. Overall it probably took a few days to get it done, but when you work an hour here, hour there, it takes weeks... but I think it is worth the effort.