All of Trisha's doodles are drawn by hand. She use pens, markers, pencils; just the basic stuff. She lets her hand take over, and when she finishes a doodle she passes it on to me; her design assistant; she calls me her Right Hand Nat.
I then scan it and turn it into a printable image that is ready to color.
In this age of computers doing and running everything, I thought you'd like to know the most important step in creating Trisha's Abstract Doodles does not involve machines. -Nor China! :D