any one familular with street sharks?

If your going to use a normal brush add some liquid latex to the paint, that way it will flex and won't crackle. An airbrush could work too, I used an airbrush to paint capes before I heard about the latex method. Make sure not to over do it on the paint though, if you spray too much on it will crackle. A light coat or two will do it. At least in my experience.

So using a normal brush would be best? Because I was thinking about using my air brush.

add a few drops of liquid latex to the paint.

I have had good results mixing acrylic paint with liquid latex or plastidip as per the tut on Jins site.
Might try that

my advice:don't use enamels on the soft rubber parts.Actually don't use enamels at all.