I garden quite a lot, in fact have done it professionally. So I get the hands problem, some of which just goes with the territory.  However, recently I have noticed that if I keep a bucket of water with me when I am working and occasionally rinse my hands in it as I work, my hands don't get quite so stained (nor do the handles of my shovels get yucky when I am working with compost). Also, when I go inside I clean my fingernails with a brush, warm water & dish soap...