I used to think it was crazy that hand models would wear gloves all the time but I suppose it actually makes sense when your paycheck depends on you hands looking perfect. I think there is a lot of pressure in parts modeling to truly have flawless "parts," or hands in my case, so the upkeep is kind of intense.
I have never really been that into moisturizing but I've started to embrace certain lotions and oils. In particular I think the number one hand care essential product is a good cuticle cream. I never cut my cuticles unless they are crazy dry or I have random hang nail. I'm not certain that this is medically accurate but I think cutting your cuticles can make them grow back more jagged and hardened.
Product wise, I like anything Burt's Bees, in particular the Lemon Butter Cuticle Cream and Hand Salve. The cuticle cream is an instant fix for dry cuticles and the hand salve is the most moisturizing thing I own. I like to do a combo of the two products and if I have a shoot the next day I'll put them both on and wear some overnight lotion gloves for extra softness in the morning.
Another super important thing that I had to learn the hard way - ALWAYS use a base coat when painting your nails anything highly pigmented...there is nothing worse than waiting for your stained and nasty looking nails to grow out. I like Sally Hansen's Double Duty Base Coat and Top Coat because it is two in one and lasts a long time.