This is what we picked up for a similar purpose:
http://www.amazon.com/CS-Hyde-Polyet...ords=UHMW+tape
UHMW tape with adhesive back - only .020" thick, easy to apply, and offers a slippery surface. Not sure if the teflon tape that Bob mentioned would be more slippery, but the price was hard to beat for a 18 yard roll.