It's not your English Marcin, I don't know what "focusing rails" are either
A couple of questions :
What is your diffuser made of?
Do you use minimum aperture, or the next stop up? Some say results are better if you don't use maximum or minimum aperture, but go to the next stop, and I just wondered what your thoughts on this issue are.
Do you use single shot, or rapid fire? Or maybe both?
I'm interested that you do not use a tripod - as you say, they're just to quick for that kind of setting up. It just goes to show that sharp images can be obtained without a tripod, I'm impressed.