I needed an extra pair of cottages on the end of the terrace with the pub and corner shop, I had already modified the pub to straight instead of corner and had scanned and printed one of the Metcalfe wall sections for that  so for this further extension bought some Metcalfe Stone card and fed a silhouette of the scanned wall to the plotter cutter, measured up the space I needed to fill and shortened it to fit.

The big noticeable difference was the lack of lintels and cills, scratched me head (carefully to avoid splinters) came up with using thin strips of self adhesive paper or vinyl, the A4 vinyl sheets I use have a margin that doesn't get printed so I sliced a narrow strip off the edge of a sheet of vinyl and stuck a long piece in place over all then trimmed it.  So before during and after in the pic. Note how badly the Metcalfe card cuts in the plotter cutter, needing attention with a craft knife to clean up, most other card cuts clean.  It's still quicker than cutting it all by hand though!

Although I model in OO gauge, I use Evergreen & Slaters Plastikard to scratchbuild all my buildings, detail work such as you're on about I use these Evergreen plastic strips;-




http://www.evergreenscalemodels.com/Strips.htm#Dimensional



Some small enough for N gauge.The best local retailer being Westbourne Models.

Yeah I use Westbourne Models quite a bit for plastic and brass with the exception of round or square plastic - hollow and solid, that I get from an Ebay Chinese shop 48 x 500mm long pieces for £11.99, only need to buy other sections locally, "L" "H" and channel etc.