I have just started tampering in the painted signs department. It really intimidated me to use a stencil and make sure the paint didn't bleed under the vinyl. But I have a few tricks that I tried that worked amazingly well for me!
I first designed my stencil in my Silhouette
I then cut out the stencil on Oracle 651 vinyl (an outdoor vinyl that is stickier) and placed it accordingly on the pallet. I then applied a thin coat of Mod Podge over the letters to seal the edges. After that has dried, you want to paint with an almost dry foam stencil brush and use a dabbing motion until everything is painted. (Stencil Brush like these) Let the paint dry slightly before removing the vinyl stencil.
I made this circular sign the same way as above. I did my design in my software and cut my stencil out to fit the sign.
My wooden sign I used was the bottom of a whiskey barrel that had broken. It was a little trickier to do this sign since I had to cut it in several pieces to fit this size of sign.