Blackening Edges of Objective

Okay, we've all heard that this is a good idea. So what does everyone use to do this? I've used "Magic Markers" on smaller lenses. Is this okay for bigger objectives? I worry about outgassing and always let the lenses I blacken with MM sit out overnight before reinstalling. Other options?
Thanks,
Bill in SA

There is usually a retaining ring holding the lens in its cell, and the objective is larger than the clear aperture. Since the edge of the lens is hidden behind the retaining ring, how is light going to reach the lens edge, and why would blackening the edge make any difference in performance?