I used to run a speed control... but it seemed to kill the grinders faster. The windings aren't dialed for the lack of amperage?? Regardless.. i thumb the grinder on and off.... i use a slow drill with my 1/2 for detail and guide bowl widening.. it removes quite a bit for the speed.
At some point I'll post a video of me just doing a port And I'll bet I get some funny responses on how i go about it.
Grind on!