Most printed objects need sanding once they're out of the printer, but it's often tricky to get into all the shapes with raw sandpaper. I made up these sanding tools which I printed, sanded, and then glued bits of sandpaper to the shaped heads with PVA glue. The PVA holds well enough for sanding if you wrap a bit of elastic around the head while it dries, but when the sandpaper is used up, you can still peel it off and replace it.
I intend to print a set of these out in a few different colours when I get some more filament, and match each sander to a grade of sandpaper, so I can get progressively smoother.
For some reason, the concave head wouldn't export properly as an *.STL file, so I had to split it into a head and handle. Plastic glue holds the parts well enough that it's strong enough to sand with.
I've included the original blender files, so you can modify these in blender if you need a customised sanding tool for a model. You may also be able to get the concave tool to print out in one piece.