Cleaning brake calipers and carriers - best tool?

I figured someone here will probably know: I have removed and disassembled calipers and carriers from an early 00s car. They had never been cleaned in 19 years and 90kmi, so there is a fair amount of rust and brake dust on them.

I tried an ultrasonic parts cleaner with Evaporust, a combo which usually gives pretty good results, but I haven't gotten very far.

After that I put them in a vise, took the drill and (several) brass wire brushes out and proceeded to try cleaning off the worst of the stuff with those, intending to give them a second dunk in the parts cleaner afterwards.

However, the work is very time consuming, geometrically difficult (getting into the various areas is hard to impossible) and honestly not that astoundingly good from a results perspective: most of the rust seems to come off, but there remains a weird black deposit which, however, doesn't seem to be brake dust because a) it's thick and b) it doesn't come off even with a chisel... so it almost looks like the steel is selectively leaving carbon deposits down?

Would I be better off with a sandblaster of some kind? Are the 'open' models any good for this type of work or should I look for a cabinet? I have four calipers, four carriers and then I have the knuckles etc that are on the car to treat as well.

As an alternative, could I use a grinder with a flapper wheel? The problem there of course is accessing anything that is concave...

Looking forward to suggestions, insults etc. #GeneralToolDiscussion