Duck tape and WD40 fixes everything!!!
I learned silk screen when 15-yrs old in Jr. High School..(1967)
I would first--research the use of heat..maybe warm your textile paint..
Maybe use a HEAT-iron first--on the TEE-Shirt..
Possibly--you need a solid surface below the print area(the TEE)..
Place a piece of hard wood..inside the TEE..only allowing a single surface to strike the silk.