4b) Sacrificial Layer (optional): On the hull exterior, to be done instead of
: 4a) Lay on one more layer of cloth and do not fill the weave. Instead,
: when you sand the boat prior to varnishing, just sand the cloth smooth. It
: will lose its structural strength, but will add abrasion resistance.
: Supposedly this method also makes that sanding job quicker, because less
: material needs to be removed -- it isn't as lumpy as a layer of 6-oz.
: that's been filled with 3 layers of epoxy. Downside: costlier than a thin
: fill coat.

Not to sure about this idea, you'll leave yourself open to the infamous "print through" problem, several months later. This is one of those "been there done that" things. The attached article covers this quite well, with test results to back it up.