My most used sander for risers is my Rigid oscillating belt/ spindle sander. I like to grind a notch in my shelf to give some more clearance for the fletching, so I do that with a round rasp and a small half round rasp that I bought for carving. I do most of the sanding by hand. Not that I like sanding, but it just seems right on a riser. I have a Grizzly 1/2” X 18” sander as well. I used it when I built a two piece take down bow. It would be good for the sight window, but I usually forget I have it. 🤔
I also have a Dremel oscillating saw/sander with a nice triangle shaped sander. I like it for getting into tight corners.
Dave.