I have read a lot of discussion on this topic on wood forums from guys that make small wooden puzzles, beads, etc..... seams to be very poor results as far as what I would consider a sanded finish. Seams relief of sharp edges and giving an overall "softening" to get a worn/distressed look is great but it isn't an effective method for any sort of decent sanding. Nut shells, garnet, strips of sandpaper, plastic beads, abrasion blocks, and other items utilized in tumblers, some try using shakers, and plenty of examples of loading up pieces with 1 inch pieces of sandpaper and doubling up in thick pillow cases and chucking in a dryer.
Another issue is lip slots would likely need cutting last along with any ballast holes.