i assume you are using water based inks, because you can't iron plastisol. it doesn't really work, you can't get an even & hot consistent heat set this way, most water based inks will self cure after about a month. or you can get union aerotex inks which self set in 24hrs.

or use your home oven & a big cookie sheet, heat to 350 then put in the garment, for 3 min & remove. to be sure you will need to get a temp gun, i've seen them for as cheap as $30 some places, this way you can test the ink layer for the right temp. it needs to get to 300 degrees. ovens vary, test with junk prints before you get started.

www.chaosprinting.com