I don't have any experience with shellac bought in flake form but I am curious what would happen if you reconstituted them into a big mass. Bunch all of them together and heat them up. If this is successful perhaps the shellac can be used after all.
Get some self adhesive 3M tape and make some buff sticks. Don't use a mop as you'll round the edges. Get the equivalent of 200, 400 and 800 grit (I can't remember the micron equivalent, so look it up) and see how you get on by experimenting on scrap cases.