Wigglers and Tricks

You can make your own wiggler with a peice of chewing gum or clay
and a small steel needle (like from a wood moisture meter). Stick the
clay on the end of the endmill you are getting ready to cut with and
stick the needle in the clay then use like a regular wiggler. Find your
center then take the clay off and start cutting. Make sure the needle
is small so if it flies out it won't matter. But it won't fly out.
Obviously not the most accurate or desirable method.
Another must have item is an Optical Center Punch. It is the best
fifty bucks I ever spent and it is the closest you will ever get using
scribe lines and punches.
The only remaining trick with the wiggler is finding the center of
an already made hole. I would like someone to tell me how this is done.