Freehand can be a fickle beast. The best thing you can do is take your time at it. Before I ever put any freehand on a banner, skin, or any sort of surface, I make sure to paint the object as normal. Many people, including myself, get bent out of shape about freehand before they even start; they panic about getting everything to look just right. Go into painting the piece as you would any mini. Take it one step at a time.
I usually start with basic shapes for my freehand. Identify the main shapes, and "sculpt" them into form with your brush. It could take a few layers, but take your time with it. I usually do this step with a base color of the design I'm going for. If you make a mistake, don't worry, just use some of the background color to act as an eraser.
Once the basecoat is down, you'll notice it doesn't look right. Nothing to panic about, it'll get much better when you had your shading and highlighting. Slowly work in your highlights and shadings while keeping with the overall llighting of the rest of the model. If it doesn't look right, just keep inching until it's spot on. It can take a while and takes a lot of practice, but when you'll get there, you'll be happy.
I hope this helps.
All the best,
Jake
(Got a good 50 of em stripped )
