This is a pretty simple instructable, and many users have skills far beyond what is covered here, but I am making this instructable as a way to show a really quick, efficient method for doing rough screen printing. A lot of people might already know all this, but it took me some experimenting to get it down.

The steps are not that complex, but there is a few quick tips inside for when you just want a cool, repeatable stencil in 5 minutes. It may take you more than 5 minutes to read this, but once you got it down, you can really start cranking out stencils for all sorts of things! I have access to a nice silkscreen machine, but i still use this!

For quick overview the two main tips are:

Drag your eraser through your outlined text (for quick "stencil-ification")
Use two colors of spray paint for sharper edges

Materials:

Access to a laser cutter
Vector Software (I use Illustrator, you can use lots of free open-source alternatives too!)
Spray Paint (Two Colors! I'll explain later!)
Paper or really thin cardboard (like cereal-box thin)
Something to spray the stencil onto (A wall, a shirt, a millipede terrarium)
Tape (I found this nice 3 inch masking tape at Ace Hardware)

Step 1: Create Image

Put together the images or text you want to create a stencil from. In this example I am making a stencil to spray on the top of a terrarium for a millipede named "Konrad" (after Konrad Lorenz).

So I have text and a full color image that I got from the internet.

Arrange them how you want in the graphics editor.

Step 2: "Stencil-ify" the Text

Text is always tricky with stencils since floating inside areas (like the middle of a letter "O" or the top of an "A" ) get dropped out. My ultra quick solution is simple to drag a line through it.

*Tip Erase a line through your text for stencil-ification:
First you need to turn your text into something that the eraser tool will work on. Choose "Type>Create Outlines," and all your text will turn into editable shapes.
Next, choose the eraser tool ("Shift+E"), set it on a small diameter, and drag it through your text. If you hold down the "Shift" key while you drag, it will constrain your erasing to a straight line. Just drag this line directly through the middle of your words to free the "islands" in the letters that would get lost!

Finally for your color image, click the "Image Trace" button in the upper left to get a quick silhouette. You may need to adjust the threshold to get the image to look how you want. If there are "islands" in this image that you want to liberate, you can use the eraser technique again. But for speed's sake, let's just go with it!

Step 3: Laser Cut

Use the vector cut mode, and set to a high speed and high power. Load in a piece of paper or thin cardboard (think cereal box). The thicker the stencil paper, the more error you may encounter when spraying along the edges. Your paper is thin and should blast right through. Very quick cut!

Make sure to position your design in the middle of your paper or cardboard, since you want nice thick margins around it.

Step 4: Tape and Spray

Tape your stencil down to the surface you want to apply the design to (in my case a plastic lid, and a shirt). Make sure to cover up any other exposed areas or else they will get paint all over them. You want all the little parts of your stencil to get as flush as possible. For things like my shirt I had to lay weights like rocks and stuff on top of them to help keep everything flat and together.

*Tip use TWO colors of paint:
the main problem with these types of stencils is that the edges can be ill-defined (fuzzy looking), if they are not all completely flush against the surface. Even with lots of work with different small weights and tape to hold the stencil flush, there will still be areas that might not be completely flush. I have found that using two different colors of paint (a black undercoat, and a blue overcoat), visually reduces the fuzziness along the edges since one coat may have been sharp in an area where another was fuzzy.

*Tip Spray from one angle:
Hold the can directly above the stencil and sweep your arm past in a lawnmower-like motion. Don't rotate your wrist or this different angle will spray up under the stencil in certain exposed areas.

For the big shirt stencil, I used cereal-box thick cardboard, and two slices (so it would fit in my laser cutter)