I've done several sets of bars with cloth and shellac. I'm not sure of your first question. Does it absorb, what?

Cloth tape absorbs a couple of coats of the shellac before it beguns to build up. I didn't see it as time consuming. It took a few minutes to add a coat to the bars every few hours. In non-humid weather it dries quickly, in humid conditions it might take 4-8 hours.

Once coated the shellac cotton bars don't seem to absorb any water or sweat or anything. I've gone 2-3 years without doing anything. They resist dirt much better than the imitation cork I've used. They just don't look as grungy after months of use.

I find they the shellac and cotton feels more grippy than cork when wet. I've ridden in hours of rain and had no trouble with the shellaced cotton. Maybe it wears the shellac off faster, but I've not noticed.

So I think it looks better longer and is just as good as if not better in the rain.