If I put a bedding block in my rifle do i have to glass bed it also. And if not which process is more accurate.

No...I would just glass bed but that's just my opinion. If your stock is on the cheap side you might maybe consider dropping a couple pillars in though.

Hmm...what are pillars and what do they do.

Pillars are usually aluminum sleeves that are installed through the action screw holes. The screw holes have to be drilled out to make room for the pillars. Pillars help keep consistent tension on the action screws (wood shrinks and swells, etc.).