Why one day
A studio with three artists on four-to-six-month waitlists is a studio that is effectively closed to anybody who has not already decided to wait half a year for a tattoo. That is a fine business and it is a bad room: the people who walk past, who are curious, who want one small thing, never come in at all.
So one chair, one day, staffed out of whatever capacity exists that Saturday. It is not profitable in any direct sense and it is where a meaningful number of the booked clients first came through the door.
What to bring
An idea rather than a plan, and a placement. The whole point of the day is that something gets drawn on the spot, which works when there is room to draw and does not work when you arrive with a finished specification that needs discussing.
Also: ID, patience, and something to do. The sofa is comfortable, there is coffee, and Tab will sit with you whether or not that was your preference.
What it is not
Not a cheaper route to the same work. The rate is identical and the artists are the same three people. What is different is that there is no consult, no drawing period and no deposit, which is exactly why it only suits small pieces that can be resolved in an hour.
If you want a specific artist, or anything above two hours, Saturday will not get you there faster. It will get you a good small tattoo, today, from whoever is free.