Tattooing would follow the same basic concepts described in Art Creation, with the addition of another required stat: Body Alteration. If you attempt to tattoo without Body Alteration, your difficulties will be 2 higher than if you had the stat. Yes, anyone can poke an ink-dipped needle into skin, but the +2 diff represents the difference between a teenage home tattoo and a professionally done tattoo.

Tattoo Design: 

Dexterity+Artistry, can be supported by Wits/Intelligence+Body Alteration

If the artist is just using standard flash without major modification, a tattoo design roll is not required and it is assumed that it is a 3 success (full success) piece. 

Someone without Body Alteration may design a tattoo using normal artistry rolls, but the tattoo artist will need to rework it using Body Alteration to make the artwork suitable as a tattoo.

Actual Tattooing: 

Dexterity+Body Alteration, can be supported by Dexterity+Artistry 

Powers Use:

Powers use can be used to add successes, lower the difficulty, or allow for the use of non-standard materials. Powers use can also substitute for Body Alteration. For example, a tattoo could be created using Correspondence, Life and Matter at the appropriate levels.

Extending:

Both design and tattooing rolls can be extended as per normal extended rolling rules; however, please use common sense and only make as many rolls as required for the piece. While a portrait piece, a full-color Oriental dragon, or a multi-colored Celtic piece might require full extension, basic designs such as a black zodiac symbol or initials, simplistic flash, or a two-color cherry really only need 1 or two rolls unless the artist rolls poorly.

Failure/Botching:

A failure on an actual tattooing roll means a very poorly done tattoo. The ink did not take in places, the lines are off, or something similar. The client will definitely want to have it removed or covered up, it will be that bad.

On a botch, you get the same results as on a failure; however, you have also injured the client in some way, usually scarring. Depending on the judge and how bad of a botch it is, it may also be ruled that your inks were contaminated or equipment was not properly sterilized, causing an infection.