I had good luck just going at it with a file. The key to home gunsmithing is to go slow. The Dremel comes out too fast for many, causing irreversible damage. The file is excruciatingly slow for some stuff, but rather safe.
I reshaped my Kimber mag well a bit using some small files. It came out ok. Long ago, I had beveled the well on my Series 80 Gold Cup using a Dremel. It came out ugly.