My name is Dennis Nikolaev, I am a licensed architect, AIA member and a big fan of SketchUp.

Here are my step by step instructions for what became known as the "Dennis Method".

Preparing your Black & White image

We start by switching to the Hidden Line mode and turning off your Shadows. Make sure that your background is white.
Line up a view that looks the best with these particular settings.
Create a scene.
Export the scene as .PNG file 4000 pixels wide. (.PNG files compress the SU graphics without losses).

Preparing your Colour image

In the same scene, turn on your Shadows and Textures. Export an image with the same resolution.
That is all you need to do in SketchUp!

Compiling in PhotoShop

Open both images you created with PhotoShop and adjust your Hidden Line image to show grey lines instead of black. This will help to make it look like a pencil.

Use Copy/Pasteto place the Hidden line image on top of the textured one.

Pick up a large brush looking eraser and STOP!!!

Think....Think, what is the most expressive wall or part of your building? Only a part of this wall can show the color. Otherwise the image is not going to work. So THINK carefully what you want to see before you go on.

You will be erasing the Hidden Line layer two times with different opacity erasers. This helps to simulate colored strokes of a brush.

Finalising your image

Back on the screen you have the B&W Hidden Line layer completely covering your colored image. Set your Eraser to 50% opacity and erase about 80% of the part of the building you intend to color. Make sure that you don’t erase any of the white layer over trees or entourage – it must remain white.
When erasing, pretend that you are painting the color fields onto your picture. This will help the image look more natural vs. artificial.
Turn your Eraser to 75% opacity and go over the same area. This time cover only 70% of the part of the building that you are coloring.
Save the image, because you are done!