I love using Photoshop (or a similar photo-editing software with a painting feature) as a great way to test out pattern ideas for both pintos and appaloosas.
I like to use the paint brush tool in two ways. First, I draw the flow of the pattern in a colored line. Second, I paint with white according to these colored guidelines and then erase and rebuild from there. It's the quickest and fastest way to see how accurate a pattern idea is and how it will look on your exact model. I then print my Photoshop file and use it as a guide while painting the actual model.
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