How do I make a rustic sign from used cabinet doors?

If you plan on using your sign outside do NOT use wax. Use a poly spray over your stenciled work to protect it from sun and damp conditions. If you use wax for an outside sign the sun will eventually make it bubble and peel. If you want to use a coat or two of chalk paint over your cabinet door--you can then distress so some of the brown is showing. If there is already a coat of paint on your door then yes--you can sand and distress to show the brown underneath. Then do your stenciling. You don't have to do any sanding if you are using chalk paint as a base coat. I use small bottles of acrylic craft paint to stencil and triangular shaped makeup sponges.

Sand as much as you feel or looks good to you. Seal with at least three coats of a water based polyurethane. Oil based has a yellow tinge and does yellow over time.

Water based polyurethane spray. you can get it in either glossy/shiny finishes or satin

I agree with using the polyurethane, but I would use a marine poly, it is made for outdoor use and will protect it from the humidity and rain and heat. Use light coats and three or four coats for longevity and good protection on every inch of the signs, front and back.

Thank you everyone for your advice. I hope to have one made by Christmas. Starting tomorrow..