With Halloween around the corner I thought of creating and selling a party invitation for sale on Zazzle. I had a thought to show some female vampires in a sexy pose, but also trying to retain some menace in the design. I drew in black using a hard round brush with a dual brush setting to give a bit of texture on a 75% opacity setting. I think it's quite close to a behaving like a pencil. During the drawing I duplicate the layer and then merge (Ctrl-E) to clean up the drawing and make the lines nice and heavy.
I like to convert the grayscale drawing to blue to make it easier to "ink". The easiest way I have found to convert a greyscale line drawing to a colour is to make a copy of one of the channels (I usually use the blue channel). Then on a new layer use the Select -> Load Selection and select the Channel : Blue Copy. Click the Invert box. What you see is the "walking ants" outline of the original drawing which can now be filled in using the Paint Bucket Tool (set to 100% opacity) with the colour of your choice.