I wanted to get the jacquard paints everyone talked about so much, but ran out of time to order. Instead, I used a black paint marker that I got at Jo-Ann's. It actually worked wonderfully on the red wool suiting I used for the jacket. Didn't stiffen the fabric at all (once set).
I used a sewing marker (ink disappears after 24-72 hrs) and sketched it onto the back of mine (mostly freehand since Im good at straight lines, but sometimes used my nearby artbook as a ruler) and then outlined/filled the design in with permenant marker.
A note on that though... mine bled very very slightly. This differs mostly on the fabric you use, so if you have fabric paint you might want to use that instead. ^^
Try stenciling. Create and cut the symbol on cardboard or cardstock, then stencil onto the back. Use fabric paint. But if you're like me, and the best place to find fabric paint is two hours away, use acrylic. It'll work just fine.