K guys I know that I use my screen to screen print shirts and other things a lot. If you don't have a screen it is ok. You can go through the pain of making one which is how I started out. However that leaves you with one stencil and a lot of time.
For making your own screen you will need an embroidery hoop, some nylons and a lot of modge podge. It might be cool to say you made your own thing, however I recommend either investing in buying one (trust me you'll use it a ton)!
Don't want to buy one just yet? Well there's another alternative that I sometimes use for more of a lighter/ faded print......
Spray paint is kind of tricky just remember to hold your bottle far away from your fabric (the paint will ball up if you don't) and to hold your stencil down firm! Also Spray paint gets EVERYWHERE so make sure to cover the entire shirt so it stays nice and white and spray it outside!
When I spray paint I usually just make my stencil out of construction paper so I can throw it away after.
Here's and example of a spray painted shirt I made 10 minutes before the super bowl game a few years ago.
Total Cost: $FREE