I've tried pretty much every method and the system I use now is as follows. If the vise has a lot of rust I start with electrolysis. Then I use paint stripping gel, I just brush it all over and let it sit for an hour or so. I give it a bath with soapy water and scrubbing in a tub in the back yard. If it needs more stripping, such as a lot of different paint coats were applied or if it's just stubborn, then I repeat the stripping and scrub bath until most of the paint is gone. I finish it up with a quick media blast and then prep the metal for paint.
I've used all sorts of wire wheels in the past, and they work fine, but I like the finished product better if I do the above method.
In my opinion, do what you want and what you like to get it to bare metal. You aren't going to hurt the vise.
Edit: I wanted to add that for the machined surfaces, such as the sides of the slide, I use a die grinder with scotch discs. I might start these surfaces with very fine sandpaper disks should they just have a ton of **** on them. I'll always finish with scotch pads though.
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