Everyone shakes. What you have to do is brace yourself to minimize it and to make sure everything shakes in the same direction. You should brace your forearms or elbows against your work surface. Then brace your wrists together as you paint. If you can't keep your wrists together while still getting at the area you need to, make sure both wrists are braced on the pony so they're "connected" by it. It's a bit awkward at first, but it makes a big difference. This is what the model railroaders do and they paint on surfaces that make our ponies look huge.