Wow, I love the DPM kits, I've found it so easy to make them and get great detail in them. Unfortunately I've emailed DPM and they have basically sold their rights to woodland scenics.
For getting mortor to look real in the bricks, I paint everything before glueing. Once the brick work is painted, which I do two or three times heavier in other places, I use a reefer white, water based, testors, polly scale paint, mixed pretty heavy with water and dab it very lightly on the brick work. Once dry you can do it again with a mix of reefer white and C.P. Gray. after the brick work is done, I paint the window frames, then add the window, then glue the buildings together. Once the sidewalk and roof are on you can go around the base with a light dusting of a dark gray, hardly any on the brush and age the sidewalk and building. you can use a light sand paper on the roof and paint it for the roof, or you can actually add some light sand to the roof and let the paint work it in. Just wash the brush out well before you put it back in the paint or you for ever have sand in the paint.
As for other ghost town style buildings... Wow...
I love the Art Deco downtown buildings.. I bought mine off ebay. Though they are two of the many kits I've yet to start. There is also the Bar Mills kits too. I'll photograph what I have here in my room so you know what I'm talking about!
you can also check what this guy sells on ebay, really good work! Very haunted looking...or ghost townish..
eBay Seller: shipshape60: Model RR, Trains, Toys Hobbies items on eBay.com
I just took some photos of these kits I have..
These two are made by Downtown Deco,
This is called Blair Avenue Part two...awesome kit
Downtown Deco, Trackside Tavern
Bar Mills Saulenas' Tavern