The tools needed for painting in reverse on glass are really very simple and limited. The initial cost of the materials can be shaved down to a minimum if you prefer to start out slow. I’ll make a list of things you’ll need, and I would be willing to guess that you already have at least half, if not most of them somewhere around the house.
1) A small to medium table to work on. It can be as simple as 2 saw horses with short pine planks over the top.
2) A pane of glass with a frame that fits. If you don’t mind starting with small paintings, The local dollar store should have 8″ x 10″ frames.
3) A large brush, 1″ to 3″ wide.
4) Maybe 2 small round brushes, a size 0 and a size 2
5) manicure sticks, tooth picks, or wooden barbeque skewers
6) Q-Tips
7) A flat pallet knife for mixing paints, (A putty knife would do in a pinch) 
Clean styrofoam plates or trays, The plastic lids to coffee cans are great for this, too.
9) masking tape
10) Razor blade or a utility knife
11) Paint. It does not matter whether the paint is water based, acrylic, or oil paint. It only needs
to adhere to the glass, and any of these will.
12) Paint thinner, it’s very inexpensive, and you shouldn’t even need a full quart for one painting.
13) A few small clean rags.
