Nasty job, no fun at all.
I can only add to the above excellent advice with a small warning. I have tended to clamp vise grips on the turned lip of those clamps then found that in some cases, depending on the angle of applied force or degree of rust degradation, that the lips tend to break off. Then you’re in a real pickle.
The true key to removal is to get them to rotate first to break the rust bond, THEN they will slip off more easily. You can use a chisel, screw driver etc to drive the clip to rotate it, just a bit, back and forth until that becomes easier, THEN work on applying force to pull them free.