Are vise grips a typical way of removing those? I'd figure two nuts torqued together on the head nut threads would be a better bet. I'd be concerned about putting nicks in the head stud shank that could create a stress riser...crack. I'm kinda conservative about fasteners though. Of course, if you are replacing them, then no big deal.
FYI, I had remarkable success using O'Reilly brand foaming engine degreaser for removing paint. It took off the factory stuff! The engine was pretty warm at the time, but it save me from having to use a paint stripper. I only put it on to clean off the grease, but it ended up removing the old paint I wanted to strip too. Lucky me I guess.
Camelman