X-Head Porting....

Dremels don't have the power you'll want for porting. A variable speed controller (foot pedal, if possible) for a die grinder is the way to go. Then use stones/paper. If you want burrs, get some finer toothed ones to try, but carbide ones like to blow up or chip if you overload them or if they jump. High-speed steel (HSS) won't chip as easy, but will wear faster if you overheat them.
I'd stick with paper and stones. More forgiving.