Tantoo

If you happen to have a vinyl cutter you can just send over your graphic from adobe illustrator.
If you don't happen to be so privileged you can draw out your graphic on your vinyl with a sharpie and then cut gently with an x-acto so the backing stays intact. I use a number 16 but I'm sure the typical 11 would also work.
I got a 10yd roll of white vinyl form signwarehouse.com (http://www.signwarehouse.com/c-VAVA4O1510.html) I'm not an expert in the different types of vinyl but this stuff works for me.

Now you need to weed out all of the pieces where you want sun screen to be sprayed (white skin). I weed with the same #16 x-acto blade that I cut with. I pluck the edged of the piece I'm trying to get out in order to lift it up. I then pull the rest of the piece up by hand. You need to be careful not to pull up surrounding pieces because they usually don't just come apart without a fight.

If you're hoping to have the actual graphic part burn then you should remove all the vinyl around what you drew. (example below)

If you're hard core like my friend you can remove the graphic so that everything else burns leaving a white image. (see step 4-10)

I use RTape clear conform high tack. I think that a lower tack would be better for applicaton to skin so that the vinyl has a chance to adhere without getting lifted up.
place your application tape sticky side up and then put your weeded vinyl sticker face down on top. Press from the center out evenly so that there are no air bubbles. Finally cut excess tape off.
Now you're ready to apply your vinyl sticker.

(The sticker shown is the type you'll want to use if you're trying to maintain a healthy body without skin cancer. The type shown later in this instructable is the painful inverse of this. )

Now apply to your canvas. Press firmly so the vinyl properly adheres to the skin.

WARNING: By spraying the graphic itself instead of the area around it, all your skin will burn leaving you incredibly uncomfortable with the risk of skin cancer. Please do the inverse of this shown in the previous step.

Peel away the application tape. Be careful not to lift any of the vinyl or tear it when removing the application tape. I use hard tack which makes the process a little difficult. The vinyl sticks best if the skin it's on is freshly washed and dried without oils or sweat.

Make sure the surrounding area is covered. I tore pieces of my application tape and extra vinyl from the sticker. This is much like spray painting.

If you're doing the opposite type of burn which only burns the graphic part you don't have to worry about covering up

Grab your beastly sunscreen. I use 70 SPF Neutrogena because it's not as greasy. Spray lightly so that the stencil does not get flooded and bleed under. Apply several applications for safety.

Remove the vinyl being careful not to get any of the sunscreen which accumulated on the vinyl on the skin which was not supposed to be sprayed.
When you're done you should see a slight reflection where the sunscreen was sprayed.

I'm not sure how long skin takes to burn. My friend just went shirtless all day and hoped for the best.
If you don't see a satisfactory image by the end of the day don't be discouraged. My friend was completely disappointed only to see the top part of the 09 by the end of the day.

you should have a relatively detailed image on who ever you applied the graphic to. Just be aware that what my friend did hurts like no other and is known in the state of California to cause cancer. I strongly urge you to do the inverse of what I have shown simply by weeding the border of the graphic. My friend is in severe pain right now and has a blister the size of a 50 cent piece named Amadeus.