In the past, when I shot with medium format (I'm on a 35mm kick now) and strobe lighting, I would always check my lighting with a Polaroid proof. With the last medium format shoot I did, the Polaroid proved to be an indespensable tool for determining lighting/composition. Obviously, Polaroid backs are not available for 35mm cameras (well, for some, but I'm not buying one). I remember a television piece once that featured Helmut Newton and he was using this big Polaroid camera and then he switched to his Nikon for the real photo. I'm sure there would be issues as far as composition, unless you used a lens that was the same field of view as the lens on the Polaroid camera, but at least you could get a preview of the lighting.
Is there a Polaroid camera which can be used for proofing for 35mm?