Step 4: Paint the Creeper's face
Put some of the black fabric paint on your dish, scrap of freezer paper, or whatever. Dip the stencil brush into the paint, making sure to coat it nicely and evenly. Don't get too much paint though. You don't want it dripping or getting gloppy.
Pat the brush onto the shirt and stencil. Don't stroke it like a regular paint brush, don't rub it or grind it against the shirt, and don't drag it over the edges of the stencil. Doing any of that can force paint under the edge of the stencil, ruining your nice straight edges. Just dab it up and down. Try to look at the shirt from different angles to look for spots you might have missed, especially in the corners. Sometimes it's easier to see missed spots after the paint has dried a little bit. Dab on more paint in these areas as needed.
Once you're satisfied with your paint coverage, move the shirt someplace where it won't be disturbed and leave it alone to dry according to the paint manufacturer's instructions. The brand I used said to let it air dry for 24 hours then heat set it.
To heat set the paint, wait until it's dry (a day or so), put your pressing cloth or parchment paper over the design, then press with a hot iron.
If you don't want to add glitter, you can skip ahead to Step 6.
Basically, remove the stencil once the paint is dry and has been heat set. Carefully start peeling the stencil off, working from the outside in. It should come off fairly easily. Don't forget to remove the paper from the inside of the shirt as well. You can wear the shirt now, but wait another day or two before laundering. Turn the shirt inside out before washing and follow the paint manufacturer's recommendations. My paint said to hand wash or machine wash with cool water.
If you want to add glitter, move on to the next step.