this blog which has a great tutorial on how to make your own screen print using an embroidery hoop and an old nylon stocking. I have done mine a little differently though.
I chopped a piece off my kitchen sponge to use as an applicator, and lightly dabbed the paint onto the stencil in the frame. (You can see the frame sitting on the t-shirt in the background. You can also see that I have little stubby fingers.)
Last step, leave wet t-shirts and paint all over the lounge room after realizing you have three minutes to get to school to pick up your oldest son!