I took a class several years ago called Cartooning and Caricature. A lot of the assignments were to copy cartoons. The best way to learn techniques is to study them and to actually copy them.
The following piece is based on the original from Lynne Perrella's page from her book Artist Journals and Sketchbooks (look closely for the second face).
(Based on original by Lynne Perrella)
There was only a short paragraph on the technique, so I just jumped in with my own ideas. Here is how I did the page:
1. Strathmore 400 series drawing paper (which amazingly held thru the 13(!) layers.
2. Completed covered page with turquoise acrylic paint (I used Liquitix Heavy Body throughout).
3. Mixed yellow and yellow cadmium paint with glazing medium and applied almost all over the turquoise. Splattered water over this glaze and let set for two minutes. Used a paper towel over the glaze to remove glaze leaving water patterns.
4. Blended yellow, gold, brown and titanium natural paint stamped patterns with bubble wrap, shelf liner paper, foam stamps, bottle caps and a stencil of squares.
5. Repeated #3 using raw sienna and primary red paint.
6. Gessoed page, thinned with water, leaving about a inch border.
7. Used gel medium to adhere newsprint and handmade tissue paper.
8. Painted a blend of yellow hues painted over the newsprint and tissue paper.
9. Repeated step #3 with red hued paints.
10. Repeated step #4 using browns, natural buff and yellow paint. Used foam stamps of numbers and diamonds.
11. Used gel medium to adhere and coat a stamped image (I just happened to have the stamp of the image Lynne used), scrapbook paper, a thesaurus entry for the word "clown", red and white handmade tissue paper.
12. Used purple, magenta and brown paint to stamp diamonds and circles and stenciled squares. Used a carmel apple stick dipped in paint for the small dots.
13. Mixed titanium buff, turquoise and silver paint with a liberal amount of water, pained numbers over surface.
14. Took a white gel pen (recently discover this pen - Inkssentials Opaque White - its stays on over layers of paint) to highlight the letters, face, collar and hat.
I am working on a more original version of this technique and will post when done.