Being a machinist helps. And knowing how to hand grind a drill also helps. I have bought special spot weld drills, and cutters in the past. The best thing I found was to hand grind a cobalt drill I forget the diameter, just measure the diameter of the spot weld for that, anyway I grind it to a very flat angle. I'm thinking something like a 170 degree included angle.
If that, even when using the store bought spot weld drills I still always center punch and use a center drill to make a start spot, then your drill isn't dancing all over the place.
Its not a perfect deal so using an air chisel and hammer and chisel is sometimes necessary to help separate the panels..
