Liquid Clear does have a thicker consistency than Liquid White and Liquid Black, but it does not need to be thinned.  Use a very small amount worked well into the canvas (really scrub it in!), then take a clean (lint-free) paper towel and gently wipe the whole canvas.  Touch your canvas and it should feel just slightly wet, not drenched or "slime-y".

Tip from Bob Ross Inc.