That is exactly how it is done, and even if you get a rough grit under 100 the finish is still smooth, no need to get a higher number to finish it off. And you don't have to worry it does not take off to much at a time, you are in complete control over how much you take off. Higher speed with the drill will give you more control on how much you take off than higher pressure. A sharpie is also handy to mark where more material has to be taken off and then you just sand off the sharpie marks.

Dean