yeah it's just using a tshirt instead of a towel. Towels, while big and fluffy, are actually really rough on the hair and can cause frizz or damage.
So it's basically just swapping out that towel for an old tshirt you don't mind using to dry your hair with!
you can use it to squeeze the excess water out of your hair or whichever technique you find out works for you. There is also something called "plopping" which uses a tshirt as well >> How To Plop
hope that helped!