You’re a brave woman! I’ve done more tee shirt quilts than I can count at this point. Tutorial has a lot of what I do with a few exceptions. I washed all the tee shirts before starting, even if the client told me they were clean. This may not be an issue for you if you have the shirts but it’s an easy first step. My first cut on the shirt is to go up the sides and around the armholes/neckline — basically giving me a front and back of the tee. I then do all my fusing — I use Pellon 906–sheerweight. I measure each image adding 1 to 2 inches. I then take graph paper and make squares/rectangles for each shirt. I can move them around to get columns or rows to match. I learned this technique from Lauren kingsland. I have her book and would be happy to send it to you.