My daughter wanted to have a Valentine shirt, so we pulled out the sponges, brushes, paint and plain white T-Shirt (we bought several at Michael's when they were $2 a piece). We dipped heart shaped sponges in the paint and then pressed them on the shirt. MAKE SURE YOU HAVE SOMETHING IN THE SHIRT SO IT DOES NOT GO THROUGH TO THE OTHER SIDE, can you tell I have done it before ;). We just put a magazine inside the shirt. Then we used the brush to get any white spots covered. After our 3 hearts were on the shirt, I got a brush and outlined the hearts in black.
Make sure you read the directions on your fabric paint. Ours says you can't wash it for 72 hours. We love painting shirts. We seem to do it all the time. She looks so cute with this shirt over her red thermal long sleeved shirt.