This is what I made Cainan for Christmas this year. I bought the shirt at Target, made a stencil and then mixed up some fabric paint and water, put it in an old squirt bottle and started spraying the shirt.
You can see that it is darker around the stenciled area. I went back later and sprayed the rest of the shirt a littel more and flipped it over and sprayed the back too. At first I was disappointed with the big drips coming from my cheap spray bottle but I kind of like the splattered look it gives the shirt.
For my stencil I just printed off this free image I found on Google onto cardstock then cut out all of the shaded area and left the white parts. I laid it on the shirt and started spraying. Super easy and a really cute way to personalize any shirt. This should look great with his Yoda hat. The Sith and the Jedi all at the same time. WooHoo!!