I use Turtle Wax vynal and plastic protector...gives it that wet look for about a month...I use it on all my interior and even my convertable top...just try not to get that crap on any glass, or your steering wheel...makes for a really slippery grip.
The stuff comes in a green squirt bottle...I just spray my towl then apply...it gives great results, even on my exterior trim..
Just, repete, don't get it on anything you don't want slipping, glass (it's an oil based product and hard to get off) or your paint (same reasoning as the glass)
It holds up for me for about a month. I have black interior in my convertable and it hasn't faded or cracked at all.