I made a chimney for my miniature southern country store. I first made a 3D computer model using Solidworks. I chose the Standard brick size and a mortar gap of a scale ½”. I sent the model to Shapeways and had it printed in their FUD material. After I received it, I did the usual sanding of the layer lines on the brick faces and then cleaned it thoroughly with Acetone. Using a sharp file and an X-Acto knife I added some general distressing and chips to many of the brick edges and faces (The FUD material is easy to carve).
I gave it a primer coat of flat black spray and when dry, a base coat of (Floquil brand) Polly Scale Chromate Primer. This was followed by brushing individual bricks with various brick looking Polly reds, oranges and browns. Then I added mortar using wallboard joint compound. This was wiped on and then wiped off with a damp sponge. When dry, a dusting of grey pigment powders started the mortar coloring. The final brick coloring was done with gouache and wet and dry pigment and pastel powders. Wet powders usually dry to a horrible color, but with some secondary working using water applied with a small brush and a sharp toothpick, I was pleased with the result. The mortar was then darkened more with pin washes of Silverwood or Weather-all (grey colored stains).
I added a stove pipe using etched aluminum tube weathered with gouache and powders. The cement cap was made with wallboard compound that was slathered on and carved to shape when dry.
Based on reference photos I added some questionable patching and sealing cement between the bricks and the siding. The sloppiness may seem exaggerated, but I found numerous examples of this kind of workmanship. Some of the mortar was carved out to simulate old joints that need re-pointing.