This time cleaned up, scanned, colour corrected, and composited. You know what isn't fun? A pegbar that doesn't fit in the scanner meaning you have to manually align each and every drawing. One day I'll get a A3 scanner but crikey they're expensive.
I discovered in Photoshop, in Hue/Saturation, you can rotate the hue by different amounts for each colour so you can have the whole lot be a blue, say. Then you can isolate the blue channel to make anything that is blue white! Easy-peasy solution to col-erase roughing. Writing notes in col-erase is good too because you can make them disappear when pencil testing since flickering text can be distracting.