Now it was time to 'merge' the blue/green with the red/purple to create the random pattern. In order to do this I cut each background into 36 pieces. I carefully measured them on the back and marked each square with a number. You can't see it here, but if you do this, make sure you can distinguish your 6 from your 9 etc. - I underlined some numbers to be sure.
The addition of Matte Glaze gives increased translucency and longer drying time (more time to move the paint around). I had added to the backgrounds originally - you can see how the darker green shows through the lighter green.