Icon Design

Susan Kare was the original Icon designer for Mac... this is how she produced the logos.

http://blogs.plos.org/neurotribes/2011/11/22/the-sketchbook-of-susan-kare-the-artist-who-gave-computing-a-human-face/

An idea of the production of her icon designs....

Apple

Note: this is a paintbrush. :) 

And how they progressed