I get this question way to much so this will be up forever.
Q.What tool do you use for inking?
A.Brush, thats it.

If your serious about getting into a profession that people dont know about aka "Inking" learn how to do the following:
Draw,Paint,Mastery of Elements of Design, and a foundation/eye for light/detail. I wont tell you to take art classes but
pick up some art books and study the traditional mediums before going into comic books. Also note if your crazy enought
to attempt to break into the profession pls note it is very hard and even if you have the talent you still may not get in.

Artist tips "not just inking"
Get criqtues and lots of them from all types of people(artist,non artists) and note its the non artists buying your stuff so pay
attention to what they say. You'll will be pigeoned wholed into a style until you can afford to break it and do what you want
all while being told you suck. If art is your only profession save your money and spend/invest wisely because you may sell
a lot one month and nothing for the next few months.