I find the airbrush to be the defining taxidermy tool. You have to get all the fine knife and fleshing work right, basics for proper horn & eye setting, form work, etc, but putting on the final makeup is what brings the critters to life. It's a fairly subtle thing to learn and I agree with Michelle - use as little paint as possible and custom mix your colors for the best effect.
Also, if you over paint, say get a base that is too white in the ears (not saying they're too white in your mount, just an example) I've had better luck wiping the paint back out with an acetone rag and starting over. It's quick and takes the paint right off back to the skin, prepped for the next round.
For me, the bondo method on ears is hands down the easiest way to get great ears with minimal risk for damaging the inner ear skin.