Washboard Chaz from the Ophelia Swing Band(Boulder, CO, USA-from the late 70's) which featured Tim O'Brien and Dan Sadowsky. Chaz is active as I saw him on a news feature about New Orleans a few months ago. He may have a website.

Jeff Hanna from the Nitty Gritty Dirt Band is a phenomenal washboard player. As well as every other instrument he puts his hands on. I've a high regard for Mr. Hanna. Very overlooked and underrated player/singer. Seems to me he made a washboard instructional video awhile back.