Hi. I’m building the first few structures for my HO layout (a coal tower and a couple of engine houses). I had done some Woodland Scenics DPM and other buildings for my grandsons layout and used Testors enamel paints with a brush, and Testors spray flat black or gray primer for roofs to avoid brushstroke issues. I usually soap & water washed the styrene parts first but seldom primed them. When done, sprayed with DullCoat. I found working with the solvent based paints a bit of a pain with the brush thinning, cleanup, etc.
I’ve got an airbrush in a box but am not ready to tackle it, planning to use it first on track painting.
On my Walthers 3 items I’ve just built, I tried Hobby Lobby cheap acrylics ($1 per small bottle). I thinned them slightly with water, mixing the colors to get a color I liked (e.g., wood coaling tower, brick engine house). I found that the color covered pretty well if the plastic color was not too far different. In some cases in the future I may lightly primer the exteriors if the color will be much different). I always gray primer the interior walls. I found the acrylics easy to work with and fun to try color variations. After painting, I’ve tried some weathering on the 2 engine houses with a 10:1 dilution of mortar color for brick, black or gray for grime, etc. I have yet to finish off with a coat of DullCoat, plus then add the windows material. The mortar came out a bit thin in color, so I may try next time a bit lower dilution or even the Hydrocal approach suggested as an option in one of the following threads focused on painting brick exteriors:
http://cs.trains.com/mrr/f/11/t/203842.aspx
http://cs.trains.com/mrr/f/11/t/137047.aspx
There are some links to other threads in the two above.
On staining wood, I believe the fol