My Fein tool has infinitely variable speed. It's pretty easy to control.
Also note that his windshield has been replaced.
So the butyl tape is gone, and it is probably fully cured urethane now.
That helps a lot.... as it doesn't want to seal back up while you work along.
Go-jo or soapy water works well as lube.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.