What you will need:
1. Photo. This is probably the most important thing you will need. You will probably need a few photos. Once you start editing it, you will find that some of your photos just don't convert well into a stencil.
2. A computer with photo editing software such as photoshop or gimp? I've never used gimp, but it's free so give it a try and let me know how it works for you.
3. Thin cardboard box (shirt boxes from a store work great) or 2 clear acetate sheets. These will be your stencils so you want to make sure they are thick enough to handle paint, but not too thick that it takes a week to cut out.
4. Two contrast colors of paint. I recommend acrylic. It's fast drying and cleans up easily with soap and water.
5. Exacto, or similar cutting tool. Also, get a cutting mat so you don't destroy your kitchen table.
6. Sponge or stencil brush. Either will work
7. Canvas board. These come in 8x10 which will work great. These can be found at any art supply store. Even Walmart carries them in the art supply aisle.
8. Spray adhesive. Do not use glue sticks or pva glue. It will leave gaps and make cutting the stencil very difficult.
Step 1: Edit Photo
First, pick the photo you would like to use. I chose a photo I took of my wife on our trip to Paris, for sentimental reasons. Next, upload to your computer and "stencilize" it using a photo editing program. I will not go through every step in this process. There are excellent instructables already posted on how to achieve the desired effect. Go ahead and check those out now. Don't worry, I'll wait. Go on. What are you still reading this for?
Step 2: Print Stencil
Welcome back! I told you I'd still be here. Ok, so you should have something that looks like the photo. First, drag and drop your stencil into PowerPoint. Then rotate and stretch until it is the size of one slide, or close to it. Always enlarge from the corners of the image to decrease the distortion. After you've done this, print out two copies. Yes, two copies, you'll see why later.
Step 3: Glue and Cut
Take your spray adhesive and follow the directions for permanent adhesion. Glue one paper to each side of the box or on to each sheet of acetate. If using a box, glue to the rougher side of the box. Once dry, cut out one stencil. With the other stencil, you will only cut out an outline. (Yes, I'm aware that one of the stencils is different. I didn't take a photo of this step, so this is another stencil I'm making for friends)
Step 4: Paint
Start with the outline stencil first. Follow the directions on your spray adhesive for temporary bond. Adhere it to the canvas board.
For mine, I chose Medium Magenta. Lightly dab the paint onto the open area of the stencil. With stencils, less is best, so dab excess paint onto a rag every time you dip your sponge/brush. Big globs of paint will seep under the stencil and will come out as smudges on the finished product. Remove stencil from canvas as soon as painting is complete. Don't wait for the paint to dry.
After your paint has dried, can be sped up with the help of a blowdryer, adhere your detail stencil the same way you did for the outline stencil, and repeat the painting steps with a good contrast color. I chose Mars Black.
Step 5: Enjoy
Congratulations! You just made a painting worthy of giving a loved one for the holidays. If you want, you can also apply a spray gloss as a protective finish. Acrylic paint dries to a matte/satin finish. A high gloss lacquer spray can change that. There are many products out there. Use what's best for you.