Hi Chrisk-k,
Regarding a shaky hand: First, make sure that you're using a brush that's the right size for the details you're painting. I would surmise that a 1 with a nice fine point would be good.
Second, make sure to load the brush well with the paint. That way you can make a single stroke and have good coverage.
Third, mount your figure to a temporary base so you don't have to hold it with your free hand; use your free hand to support and steady your brush hand.
Fourth, if you get some paint where it doesn't belong, don't worry. You can go back and touch up those spots.
Hope that helps.