Gather all supplies near a warm water supply. Dye kits can be purchased at craft stores that come with all of the supplies, or the supplies can be purchased individually. It is also important to ensure that the t-shirts are clean before beginning the tie-dye process.
Soak the shirts in a solution of warm (not hot) water and soda ash, or, sodium carbonate, for ten minutes. Mix one cup of soda ash into each gallon of water used for soaking shirts.
Add a couple of spoonfuls of salt to the soda ash and water mixture.
Once the shirts are thoroughly soaked, wring them out and then flatten them onto a flat surface, like a table or a back patio with a tarp laid over it.
Put the dowel rod in the middle of the shirt and start twisting it until the shirt twists into a round shape. The shirt should look twisted up, similar to a satellite photo of a hurricane, and it should lay flat.
Keeping the shirt flat, wrap rubber bands around it to secure its twisted shape. Use anywhere from five to ten rubber bands to make sure the shirt does not come untwisted. This style of twisting is optional though, and any method of twisting, crinkling, or knotting the shirts will create a unique color pattern.
Put the dye in squeeze bottles. Starting with a lighter colored dye, such as yellow, squirt dye onto the shirt, being sure to get into all of the folds, until the shirt is soaked in at least three different colors. Remember that rainbow colors will be made when the dyes blend together. Flip the shirt and repeat on the other side.
Wrap the shirt in plastic wrap to keep it moist, and let it sit at least eight hours to let the dye soak in. After time has elapsed, unwrap the shirt, rinse it in cold water, and then wash and dry it.
You can buy iron-on letters from a craft store, a fabric store, or even a computer printer. Be sure to get enough packs of the alphabet to have the letters needed to write the band's name plus any additional text desired for the shirt.
Cut out the needed letters if they are not self-adhesive peel-off stickers.
Arrange on the t-shirt while letting an iron get hot.
Press the iron to the letters and hold until the letters bond with the shirt's fabric.
Let the shirts cool before wearing or distributing.