Sponging, Ragging, Using Glazes over paint to simulate textures...

I've had some success with using two or three contrasting colors (like terra cotta, off-white, and dark brown),each mixed with liquid glaze (purchase at any paint store or home center)-three parts glaze to two parts latex satin- put into a pie plate or other small container.

After base coating the wall a color which will show through (like off-white), just brush all two or three glazes on in big, sweeping arcs (only cover an area about 2' x 2' at a time", then immediately blot with a rolled up rag, a dampened and wrung out sponge, or (best) a piece of lambswool on a handle (buy at paint stores).

Just blot, the colors will blend beautifully, and look like stone or adobe. If you want to make individual blocks, wait until the whole thing is dry, and then hand paint lines with a 1/4" or 1/2" brush. Freehand lines will look so much more natural, and it won't take so long as measured ones! If you're scared, you can chalk them in first - chalk removes more easily than pencil!! Then - when everything is dry, you can go back and add fancy stencils if you like, and maybe a few cracks here and there! Good luck!