Enzie,
I've not done a fellow artist. I think that would have it's own particular set of challenges knowing that the subject was capable of critique.
Here are a few artists painted by Everett Raymond Kinstler:
Wm. Draper 2002
Peter Cox 54 x 60 1983
Chin Chi double
Paul Resika
And these are just the painters, he has done many famous actors which you can see on his web site:
http://www.everettraymondkinstler.com/index.html