I have used the Blair spot weld cutters in the past and Chris is right about them.
You center punch every spot weld and then start the cutter at an extremely slow speed until you see a circle being formed. Otherwise the bits will chip and brake if they hit any of the weld itself.
I tried a few different types of drill bits but not the ones recommended above. They seem to work much better.
These types of spot weld removers are best when you plan to reinstall the panel and maintain a "factory look" to a restoration. As pointed out above, if replacing the panel you can save yourself a lot of time by grinding the welds down.