Scott:
The Korber buildings are looking good especially the kit bash.
WRT weathering I usually apply several coats of an india ink wash to dull down the mortar color. I then follow up with powders (black / rust etc) but very light.
It looks like the roof on the kit bash is going to be flat. You may want to try the following. Paint the roof black then either let it dry, spray with diluted white glue or matt medium and sprinkle on N scale black ballast or sprinkle on the ballast while the paint is wet. Either way once dry you will need to spray again. This gives you a really nice looking gravel roof. Sometimes I will overspray with a texture paint that has black and white flakes in it.
Joe