I have a 3d printer that uses ABS filament. The software I use will generate vertical supports for my objects before printing that can be easily broken off after they have been used during print to hold sharp angles up that would normally fall.
After breaking off the stints, the print is far from smooth. Is there a material that is best suited for "sanding" down prints without damaging the print?
I use normal wet/dry sandpaper and it works just fine. If I remember correctly, I usually start with 220 and then work my way up to 400, 600, and 800.
There are also foam or rubber sanding pads available that work really well when you're sanding something organically shaped.
The grits you start and finish with will depend on how rough your surface is.