I wouldn't call these figures absolute, or even really try to emulate them, but nonetheless they offer some basic guidelines.
The first is a rough guideline for the amount of filler required to thicken a specific amount of resin. The table is set up sort of backwards to how it might be most useful, but one could extrapolate the date they needed.
The second table provides an idea as to the thickness of single laminations of a few common types of fiberglass in a hand layup.
Source: Vacuum Bagging Techniques, Appendix B, Pub #002-150 by West System.