I've always thought T-cut is very out of date now we have clearcoated virtually everything. It was in it's element with old cars, where it could skim off a layer of paint and the car would be immaculate again. But as Jake says, if the paint is fading, you've got the clearcoat in the way.
Personally i'm giving the poorboys range a go, they seem to be very popular but not hideously expensive. And the best part is the wax smells like hubba bubba!!