There are many different techniques used on painting free hand without using pencil sketch on miniatures' surface. I'm not sure how other painters have done it.
To continue from my previous post 'Identifying Types of freehand' theory, here I will explain about my "Mind Eye" technique.
This technique I used is actually quite similar to 'flash blindness'. I believe everybody has encountered temporarily blindness when taking picture with a camera flash. That spark of light will stay in your eyes for a few minutes and slowly disappear. So same goes on my technique.
To put thing simple, take a look at the picture below:
Staring at this house for about 10-20 seconds. Then take a piece of plain paper, now look at it. Do you see the house?? If you don't see it, then repeat the process with longer time.
The picture will be the same as I've explain..... flash blindness.
So when I transfer my paper drafted design, I always put it next to me while start painting. Every time the image in my eyes wore off, I stared at the design again. Regardless of any pictures you want to paint it onto your miniatures, you can do it. But again be warn, you need to identify the type of freehand painter you are first.