McLeod's New Mutants vs Sentinels commission

From bobmcleod.com/nmsteps.html:

I started with a rough pencil sketch, to get my ideas on paper. I don't usually pencil much tighter than this if I'm going to ink it myself. You can see that I made a few subtle changes, most noticeably the change in Cannonball's pose. It was originally a pen&ink commission, but as I was finishing the inks, I decided it really would look much better in color, with Cannonball's flame and all. So I asked the buyer if he would be willing to pay a little more to get it in color. He agreed, so I started painting it with watercolor dyes, because they're totally transparent and wouldn't cover up any of the ink lines. But the illustration board had flaws in it, and dark spots  started appearing everywhere! Disaster!? Well, I just used acrylics, which are opaque, to cover the dark spots, and repainted the Sentinels and parts of the sky. I then airbrushed some darker tones to add a metallic look to the Sentinels, and finally had to re-ink over the acrylics.