The moisturizer question comes up often, and there was a rather lengthy thread about this on Genii Forum and another on the Green Monster. Brands that seem to be mentioned a lot are (in no particular order): Golden Touch, Cornhuskers lotion, Vagisil; Crack Creme; Bag Balm; O'Keefe's Working Hands; Na-PCA by TwinLab (at Whole Foods). I'm sure a search of either of these forums would be useful, as what works well is a very individual thing. It depends a lot on age, climate, and personal characteristics. The most common complaint seems to be dry hands after age 40 (I can't do Daryl's Snowshoe Shuffle anymore as a result).
As far as finger exercises, while it's true that certain card moves require building strength (passes, pinky count, etc.), I've not needed to concentrate on building specific finger strength other than practicing the sleights themselves. I did however, used to lift and worked hard on grip and finger strength with various torture devices. I'm not saying they didn't help, but I didn't really notice a difference in my skills when I was lifting. (You might run the question past Josh Jay and see what he says).
If memory serves, the late Neil Lester used to send along brochures about a finger strength building program along with the merchandise--but I could be mistaken.
As far as maintenance, Eugene Burger was amongst the first I read who recommended regular professional manicures, but that recommendation seemed mostly for appearance sake.