I did a little research last week and came up with a project that was simple and fun.
I found this site for free stencils. And on this blog for a demo. I had gone through my paint stash and all I had was 10 year old bottles of fabric paint that I wasn't sure how well they would work, so we headed off to our local art supply store to pick up some more up.
We search through his drawers and found a tee shirt that was clear of print. I line my soap molds with freezer paper so I already had this on hand. O picked out a Godzilla stencil which I traced and cut out. I ironed the Godzilla on his shirt with an extra sheet between the shirt and his went to town, very important if you don't want the paint to bleed through the back of the shirt.
We started off with a rusty yellow and within a few dabs the paint was soaking right into the blue shirt. Luckily we had picked up a few different styles. We chose a metallic turquoise and in which we dabbed it on and the paint really held to the shirt.
We let it dry overnight and the next day he tore the paper off the next day and wore it out.
We have washed it twice now and I haven't noticed any sign of wear or paint cracks.