'Caveman method' for peeling shims:
Since my eyeballs are crummy, I really need a lot of help in seeing the layers, so I take a small ball peen hammer and smash just a tiny corner of the stack of shims. This smashes them out a little so that you can more easily see the distinct layers and stab at the top shim with your fresh exacto knife blade.
Also note: the exacto blade is perhaps good for maybe peeling four or five single shims before it becomes too dull to continue getting clean single layers.