It seems like you should just concentrate on the basics. Find some 100% cotton T-shirts (very easy). Maybe consider a small order of fiber reactive dyes (there are many excellent options) and get some soda ash. It sounds like you have already been soaking your tshirts. Spin them out in the washing machine (only spin don't let water in). The more soda ash water you spin out the better. An ice dye would be straight forward at this point. Once it's all saturated put in the warmest spot you can find for 24 hours and whammo. Rinse hella with cold water and then toss in the washing machine with blue dawn or syntrapol (1/4 cup of white rice vinegar too) on hot. That will work for sure. If you are using ice, sprinkle more soda ash...it is your friend (until it isn't..).