I have'nt found a good way and still have them look very good. The finish is very thin and the fletch glue bites right into the finish, so your gonna dig the paint a little getting all of the quill off the shaft.
I use a single edge razor blade and cut it as close as you can, then a file for the remainder. If your lucky you can get the new feathers to set in the old foot print or real close.
I've considered useing clear cap wraps under the fletching just for this reason.
Good luck, its gonna take some time.
Eric