Here\'s what I did:
First, primed white; but looking back I think black would have been just as good.
Then, got a big soft brush and loaded it with Folkart metallic black on half and Folkart Silver on the other half, and went down each scale in one-way strokes, kind of wiggling the brush a little to make ripply streaks of black and silver along the shell. I let that dry; the paint was pretty thick because I was trying to make streaks. You\'ll want to do your own favorite technique for making a mottled random mix of black and silver on a model with more fine detail. Then I washed with Metallic Black to darken it up.
Then I started with the interference colors. These are acrylic art paints made by both Liquitex and Golden; the Golden are better. They are basically a colorless medium which contains micro-fine shiney dust which reflects a particular color; they\'re different from regular metallics in that you can mix them with white and they won\'t change the white to a color, but the white will take on a faint shine and the shine itself will be the new color. In this way, you can mix interference blue with red paint, and you will have red paint which will seem to have metallic blue highlights when the light hits it just right.
For the mother-of-pearl look I used Interference Violet, Interference Green, and interference Blue. The violet is kind of pinky-purple and is the brightest, so I used it sparingly. I started using a brush, making random splotches of violet, then blue, then green, then violet again, let it dry, do some more, adding some more green or blue if it was getting too pink or touching up an area with violet if I wanted a flashy spot there. After a couple layers I did another wash of Metallic Black which toned it down a bit again, and then did some more careful mottling with the interference colors. Any area that got too black got a touch up of silver and interference colors; if it got too bright it got a wash of metallic black. In this way the variety of color built up. I had to be careful not to get each blob of interference too thick; if too thick, it dried milky. If too thin, it vanished into the background of previous faint colors. You can fool around with colors and layers and such to get the effect you want; I went for pretty dark with the bulette because I didn\'t want him to look too \"pretty\".
Then I gave the shell a coat of brush-on clear gloss, then painted the body and sprayed that part matte, then glossed the shell again where the matte had dulled it. The toenails were done in a simplified version of the shell; streak of black and silver, quick dappling of interference colors, and then a wash of metallic sequin black, and glossed.