You never want to be really aggressive on the nozzle part.. too much is at stake and it is very delicate. If you reuse microfiber, you have to be very careful about it picking up debris that can scratch the head or deform the nozzle openings.
T-shirts are "celulose" which is a lot more abrasive than the manmade mirofiber. Take that into account when reusing old t-shirts. If it works for some people that's fine... but you might as well use paper towels. It's not the softness of the weave is the non abrasivness of the fiber that counts.
Seriously...$15 worth of microfiber towels from Costco has lasted me a couple of years. Why try to save pennies of a part that will cost a thousand dollars..