Have you seen/considered using these?....
Bromley Craft Products - Stencils for Dolls House Brick Finishes - Mail Order Online Shop
Use a foamboard (or UPVC as below) core for your building walls, then position the stencil and wipe over with suitable rendering (cement or polyester resin based) then peel the stencil off before the render fully cures. Overlapping is pretty easy.
For some of my buildings I have used recycled/scrounged UPVC window sill sheets. They come in various widths and lengths - some as long as the skip they are scrounged from! They make up unto pretty substantial units, you can screw the corners together and you get a decent wall depth for window and door reveals. The good thing about the stuff is that it's virtually bomb proof and it's free (when recycled/scrounged).
Just a couple of thoughts
Dave