I am very similar to Tim - 90% of the time it is my hands, or a simple piece of paper with a hole cut in it. For some more complex things, I will take a piece of paper, draw the shape of the image to be burned, and cut that out of the paper - then hold that above the print during burning.

The other thing that I do for dodging that may be helpful - especially when dodging something small like the eyes in a portrait is to take a piece of wire, and shape piece of plasticine on the end of it.