Here are the pics from the BG study I did, in case you're interested. Please refer to the post below for more accurate colors.
2. I brushed on the flat salmon color. In the future I'd use a roller to get it nice and even. You can also see the first mask I cut out of the animation cel (I pre-cut all of them from the printed out image). The cels came in handy with their registration holes. I did a trial run, so that's the sponging you see.
3. Sponging applied and cel removed. You can see how the paper is buckling (this leveled out later).
5. Two more layers of sponging applied. The light green has been masked off with another cel.
6. Dark brown sponging over the red brown.
7. While sponging on the bushes, the sponge and paint were too wet, which caused a little sloppiness. After this point, I made sure not to make the same mistake.
8. Here's a shot of the cel with shapes cut out and paint sponged on. The crazy reflection is from a funky shaped pendant lamp.
9. Cel removed to show the result.
10. Close-up of green detail lines being added (with a #3 round sable).
12. Bush details added and tree trunk painted in.
13. First layer of dark sponging and details are added to the trunk.
14. Light blue details and sponging added.
15. Dark details added again to complete the stump.
16. Tape removed! Added the last couple details before scanning (see post below).
Hope showing these steps has helped someone learn... something! I know I did. A lot more work goes into these "simple" style paintings than it may seem at first glance.