As they say, practice makes perfect.
Here are some pics of my first attempt at applying zimm. I used milliput, rolled out in powder, smoothed on with a brush and finger, then textured with a bit of styrene in an exacto handle. The pics are in a very high resolution so mistakes can be seen, but I did not find this method too difficult to achieve a result. From a distance it looks OK and when painted hopefully will produce the desired effect.
I first tried it on the front and back of the hull, then the sides and then the turret. As I progressed I corrected mistakes by trial and error.
I hope that this example will help others with this apparently daunting task.
As always, comments welcome