Since I just finished making four Mickey Tie dye shirts I will share how I did it. I initially printed out a Mickey head shape to use, however I didn't think it was large enough. So instead I used a dinner plate for the head and used a large saucer for the ears, I traced this unto newspaper, in case it didn't turn out how I wanted it to. I than traced this unto cardboard from a cereal box.
Wash and dry your shirts before you do anything else to them. 100% cotton will allow for the brightest colors. My dye told me not to use a dryer sheet or fabric softener.
I then lightly traced Mickey's head unto the front and back of the shirt with a pencil. If you only want it on the front, only trace their. You may want to try one of the shirts on to get an idea of where to place the Mickey head.
Next I baste stitched on the lines of the Mickey head shape that I traced with dental floss. Don't use a thick needle or it might leave large holes. Only sew only side of the shirt as a time. If you are making Mickey on the front and back you will have 2 tightly gather pouches when you are finished basting.
As you stitch gather the fabric. When you get to where you started pull it as tight as you can into a pouch shape. Make sure the ears and the whole Mickey head is sticking out. Wrap the string around you tightly wrapped pouch and pull tight and knot. Wrap rubber bands on top of the string. Wrap the rest of the shirt with various rubber bands.
I used a dye kit with soda ash and bottles with the dye powder already inside they came with rubber gloves and rubber bands. After all your shirts are rubberbanded you mix the soda ash with water. Soak you shirts in water about 20 minutes. Follow the directions with the dye for water amount and how long to soak.
After your shirts are soaked in the soda ash, wring the excess water out. Start dying the Mickey head(s) first make sure it is saturated with color so you get a full Mickey head. The ones with dark colors turned out better since the dye ran through the various sections. Continue to dye the shirt, make sure to get dye in the folds and have it soaked through.
Place each shirt in a separate plastic bag or cover with plastic and let the dye soak about 24 hours, more or less depending on your directions, the longer you wait the more intense the color.
Rinse the shirts with warm water and remove the rubber bands as you rinse. Cut the strings out of your Mickey head, be careful not to cut the shirt. Rinse until the water runs clear. Wash your shirts in hot water and than dry.
I hope this helps.
Becky
I was told to use waxed thread, and when I asked for some at Wal Mart, I was basically given a spool of thin fishing line. 
So I gave some thicker fishing line a try, but it broke when I pulled it tight. I then tried dental floss and it worked great! I thought it would be hard to pull thru but it was not. 
I thought the banding part was the hardest--getting it tight enough and thick enough. The thicker the bands are, the more white that shows and the less bleeding of colors.
give it a try and live and learn as you go along. 
But their shirt were really cool... 
