With a whole week off around Thanksgiving, Ouliana and I finally had time to test out a method for templating bleached shirts we'd seen online. It needs freezer paper, which as far as I can tell is butcher paper with wax on one side only. The plan consists of cutting out your pattern, and ironing the waxed side onto the shirt, applying your bleach-water solution, and peeling off the mask. The twist being that cutting precise patterns is a pain, but a laser should be able to make quick work of it!
For the pattern, I came across this image of Samus from the Metroid games, posted by terrorsmile on DeviantArt. I wanted the pattern to be a true stencil, meaning having at least one totally contiguous region to be the "mask". That took some doing, about an hour of work in GIMP, but I ended up with an inverted stencil that could be cut without producing "islands". I'm a bit reluctant to share the file, as it's based so closely on someone elses's work, but the process is fairly straightforward (the magic-wand selection tool will immediately show you any "islands" left in your image.)
The other issue that came up was the freezer paper tends to curl (it does come on a roll), so it had to be taped down at the edges to a rigid substrate, scrap acrylic in this case. The second pattern was a manually made stencil of the "doom guy" dolls from the 2016 Doom game that Ouliana made, seen getting ironed on below.
The positive-stencil of the doom guy did end up having "islands", meaning a few pieces of freezer paper had to be carefully place and individually ironed on. Also, having a positive pattern mean needing to block off the rest of the shirt with extra paper to prevent any stray bleaching. The negative stencil, shown below just after ironing, needed no additional masking.
I opted for a slow and regular application of 50/50 bleach in water solution, spraying a few times, and giving it 5-10 minutes to act and dry, and repeated that roughly three times. The shirts were then rinsed out in the shower, and immediately washed. We noticed that setting the iron too low resulted in poor bonding, so the paper would "pop" off the shirt, and ironing too hot resulted in small beads of wax around the edges of the stencil that remained after peeling away the paper. They can be picked off by hand, but it is a pain. The final result of my shirt attempt is below!