After I got into this drawing I realized I was going to have problems showing the strings. They appeared very light against the dark fret board of the guitar. I fussed around with erasers, thought about how I could show the strings with white paint, thought of faking them and putting them in as dark lines, and suddenly I had an inspiration...use heavy duty white sewing thread! So I did a trial run and it worked wonderfully well. It is somewhat unique for me, as I rarely do mixed media.