wacom is usually the way to go, but it's more about the software then the input. not all of them give good results to make a painting. from there it's all about skill, since your looking at the screen and your tablet is flat on the table, it may take getting used too. if you get a large tablet, you get more fine detail, but you also have to move your arm more to get across the screen. the smallest one usually has the fewest features, i usually get a 6x8 or something like that, and often work in a small area of that.
---Mike Savad
