Also, the dremmel with a stone is just to get a hole started for a drill bit, don't try to bore a deep enough hole for an extractor with the dremmel alone. Also make sure you protect the opening to the crankcase with some clean rags. if you drop any broken bits of stones or a small drill bit, even metal shavings, it could be bad news.
If you're even thinking about cutting a small slot with a carbide disc, it must be done very carefully as not to deface the head! you could easily mar the surface with a slip, so decide to do this with good consideration. The disc is a very small (about 1" to 1.5" diam), somewhat brittle wafer, half as thick as a worn dime. They'll be in the dremmel bit rack at the hardware or hobby store. They want to track away while in use and must be held very still while cutting as they can break apart pretty easy and go flying (wear goggles).