Hi Scott, There are a couple of methods. Sublimation printing transfers only the ink to the garment but is limited to light colored polyester garments. You will also need to buy a printer and sublimation inks.
I believe there's a method called image clip which is a two step process. The first step removes the polymer by heat and then the transfer is applied to the shirt. I've only seen this demonstrated with a laser printer but there may be something for inkjet, I'm not sure. The paper is very expensive.
My solution was to purchase a cutter with an optical eye. I use reasonably priced professional paper and pigment inks and let the cutter do the trim work for me. I've been having excellent results.
I hope that helps.