Enzymes dissolve the cells and are therefore gentler than other exfoliants. Enzymes are the best for sensitive, reactive and acne prone skin, since there is no scrubbing to cause irritation. Anyone can use an enzyme exfoliator.
Many people believe in daily exfoliation (men shave daily and look at their soft, supple skins, apart from their foreheads which they do not shave!). I like to exfoliate at least twice per week.
If you like a scrub exfoliant, it should only be used when your skin is softened and warm. Use your exfoliant after you have cleansed, never before.