My Dremel is an older one: mid-nineties corded model with a slider switch on the side for RPM. Seen all kinds of use, and still going strong. I'm told Dremel's construction quality has since fallen down the "planned obsolescence" hole.
I got a foot pedal for it back in the day that has a rheostat switch instead of a momentary or toggle switch, and that's been gold for manually controlling the RPM. The slider on the side of the Dremel bottoms out out an RPM that's still fairly high, and I don't have true "on the fly" control with it. But with the pedal switch, I have full real-time control over RPM from zero to top speed, just like with a cordless drill's trigger.
If you have a corded Dremel, I highly recommend getting a pedal switch like that.
I used my Dremel to polish the needles for my Eclipse and SOTAR. I strapped it in a bench block first so I wouldn't have to worry about the number of hands I have available. The needle sticks out a lot from the chuck, so it's super important to use one hand to passively grip the needle (firm enough that it can't deflect, but not so tight it can't spin freely) further down it's length AT ALL TIMES, otherwise it WILL spin out and bend from centrifugal wobble. As long as you're mindful of that though, it all works fine. Having the pedal switch helped a lot, both because I didn't need to take a hand off either the needle or polishing rag to start or stop it, and because it allowed me to ease the RPM carefully up from zero to whatever felt comfortable/safe, rather than instantly exploding to whatever the slider was set to.
Contextually irrelevant side note: I've always REALLY wished Dremels had a switch to control motor direction the way drills do. If you're right handed, the direction of the motor often has it spraying the dust/particles from grinding or cutting directly toward your face instead of down or away.
