I’ve tried using an air powered die grinder and I didn’t really like
The power level was really nice, but there didn’t seem to be a good
way to adjust the speed on the fly. The tool itself was cheap, but it
also takes a HUGE compressor to keep up with the air consumption.
I also have a couple of polishing lathes. I use them when I can, but
for a good chunk of the work I do, a flex shaft is either required or
makes the job far easier.