I was not aware of the "Rain Machine" in Telecine. Perhaps it was the "new improved model". The one I remember was a device used from the studio floor. It consisted of a barrel like horizontal drum with a center axle that could be rotated by a hand crank. The drum was covered with Emery Paper (Not Sandpaper). A spotlight was focused on the rotating drum (perhaps an "Inky"). You had to be careful in what direction you rotated the drum, otherwise it might be raining UP instead of DOWN! A regular studio camera was used to pick up the tiny white specks reflected from the Emery Paper. There was no Matting in those days so th TD had to split the fader arms in order to superimpose the "snow" over the scene.