I've tried several ways to shine up a faded poptop, especially the colored
poptops (blue, red, gray, etc.),  short of a sand-and-repaint.  The easiest
and best that I've tried is a product called 2001.  Easy to apply and the
restored appearance lasts for months.

I don't recommend using car wax on the poptop.  Traces of it tend to stick
in the low parts of the grain and are very hard to remove- plus the
appearance isn't that much improved.

Bill
www.geocities.com/yosemite/gorge/1706