Bonnie Bonnell & Joe Wall from the American Museum of Visionary Art (Baltimore) give a talk about the creation of the mosaic mural there. The whole video runs about and hour and fifteen minutes.
Bonnie's written instructions for the double-indirect methods are available here as a PDF file.
This project is being lead by the local nonprofit Art For The People in conjunction with The City of Takoma Park & the Takoma Park Foundation of the Montgomery County Community Foundation.