Wash new T-shirts to remove the sizing and make sure older T-shirts are clean.
Pinch the center or intended focal point for the swirl with a clothes pin. Make sure the pinch is tight. For extra support, tie a small rubber band around the center pinch about a half-inch in.
Hold the clothes pin straight up and down and hold the T-shirt flat with your other hand. Begin to twist the clothes pin like a door handle, making sure to keep the shirt flat with your other hand.
Wrap at least three rubber bands to keep the roll intact once the whole shirt has been twisted. You might have some stray shirt peeking from behind the rubber bands; you can choose to leave these or pinch and twirl little mini swirls.
Follow the bottle directions for mixing the dyes and have all mixed dyes at hand. Put on your gloves. The roll should resemble a pie in that the rubber bands create little slices. Use a different color on each slice. It's OK if colors bleed together a little bit.
Wrap the shirt in plastic wrap or a plastic baggy to keep the dye moist. Do not remove the rubber bands. Let sit in room temperature overnight.
Cut the rubber bands and hang the shirt up to dry the next day. Wait another day and hand wash your shirt.