Q:

What can I use to preview Pantone tints?

is there a Pantone book that shows tint values  eg. 20% or 40% of 021c?  I have looked far and wide for a Pantone Tint Selector which I seem to recall was available many years ago but now I can't seem to find it.
How do you get around this problem of tint values?

A:

I guess this pack is what you are looking for. It shows tints of all Pantone inks in 10% increments and some more, including reversed out text and some overprinting.

