Topical medication absorbs quite well through most skin- it usually contains chemicals to increase permeability. Skin is also naturally extremely permeable to chemicals- the thickness doesn’t make much of a difference, as long as you avoid callouses (which might prevent absorption).
If you want to avoid wasting any, the only really significant tactic would be to avoid areas with hair, because some will get on the outsides of the hairs and dry there, not being absorbed.
Follow the directions. Do not apply it anywhere it says not to apply it. And as with anything containing alcohol, avoid sensitive skin areas and mucus membranes unless otherwise directed.