The glassboard which is suitable for telescope bearings has big bumps all over it making it totally unsuitable as a white board. Don't try to use smooth plastic on your telescope. It will be too sticky. Of course if you are only building a small telescope for use at low powers, then just about anything will be good enough. Which is why Coulter Odysseys come with nylon toilet seat feet as altitude bearings, and a low power eyepiece. The first thing I did to my Odyssey II was get more eyepieces and put in teflon on beige tweed Formica bearings (alt and az). It made a significant improvement.
Chuck