to have success with the vise grip method this is my advice.  buy a pair
of curve jawed vise grips.  leave them in your tool box and only use them
for operations such as this.  you don't want to be dulling those really
sharp teeth on the curved jaws.

before you put the vise grips on get a punch and give the head of the
fastner 100 short high hertz taps with a hammer and punch or a hammer if
you have room.  then put those vise grips on as tight as you can close
them will both hands and all your mite.  that should make the teeth cut
into the fastner enough so that you don't get slippage.

also i think craftsman and snap-on make a tool that goes on the outside of
cap screw heads to get them off when they are stripped.

jonathan