Software workshop 3 : Halftoning collages

Something I really wanted to find out from these workshops was how to screen-print black and white photographs with drawn elements, since I often work in collage using both of these elements together. So...this how you do it: 

• Open collage in photoshop and divide elements into 2 layers according to colour. 
• Copy and paste black layer (one with photos on it) into a new photoshop document. 
• Convert this document into 'grayscale' mode - this will merge the black layer and background into one. 
• Then (as before) go onto 'Channels' and add 'new spot channels'. Copy and paste 2nd colour components from collage document, into the spot channel layer. 
• In order to get the best effect you should 'fill' the 2nd colour components with black before copying and pasting them in - that way you can adjust the tone as you please in the new document. 
• Another way to do is not to copy and paste the 2nd colour components in, but simply draw them as you would when creating a usual half-tone image. 
• Then (as before), 'place' this document in illustrator and use the printing process spoke about in the second software workshop.