I recently purchased Statue Vanish by Roy Kueppers. It is such a great effect. My only issue is that the gaff coin has a much more DULL patina than the other quarters. Is there a way to even those out? Polish the gaff, or dull the others?

If you do a quick search around the cafe, there are a whole bunch of threads on lightening or darkening coins. Most of them are about silver coins (e.g. adding patina) but most of the cleaning products and techniques will work just as well on the clad coins.
Just remember that for clad you don't want to try softening - or much in the way of using sandpaper/steel wool, since if you take off too much of the outer layer, it won't be the same nickel outside.

My suggestion would be to polish the dull coin up - it's much easier to get a coin shiny than to match another (shine them both) it is to darken one coin just the right amount to match a second one.

Agree wirth poiishing the dull quarter.

Try Nevr-Dull.

Can anyone comment on the sneaky bandit? Does it go on your sleeve? Your hand?

It is designed to be concealed in your hand but with some imagination you can place it wherever you feel it will work best for you.