I've done some seraching on the forums and did find some interesting posts about diffsuison printing, as I am going to try that process soon. I'm going to be using black pantihose to give it a start. However, I never saw any mention of wether the diffusion material such as the hose is held stationary under the enlarging lens or is it moved about, or does it matter at all.
If it's close to the lens it'll make no difference moving or stationary. Held near the paper theres a chance of texture of the material showing if held stationary.