Blu -Tack Under Bookshelf Speakers?

I heard that Blu-Tack is a good substance to put between bookshelf speakers and stands for absorbing resonance. How much would I need to use on a 8"w x 11"d speaker on a 8"x8" platform? Do similar substances like FunTac and Elmer's Tac n' Stick work the same? (I'm having some trouble tracking down the original.)

Thanks in advance for any advice.