Hello & welcome to the forums!
One thing that may help the 'shakes' is to mount the subject being painted on a handle such as a block of wood. Brace against the edge of your work table and keep the hand holding the brush near the work, braced as well.
Think of the control holding a pen close to the paper, you are only 10 mm +/- away. Same goes for brush painting.
Another technique is to simple practice a few brush strokes on a scrap part to get the feel of your paint and brush, this may help the 'commitment' fear of applying paint to your latest model.
Most of all have fun and I am sure your skills will improve with some tips & practice!
Jason