Rub this on with a small paint roller a twice a day for the 3 days leading up to a track event. It works. I dunno how long the effect will last if you're using it on the street, however.
The Phoenix Racing tire expert that is on here also said there is another product called "Goat Piss" that works just as well.
FWIW my Pirellis seem hard as rocks after 18k miles...they were pretty good new but I think they just harden up over time.