Glad you all liked my crazy antics
I've always loved infomercials... the crappier the product and the stupider the claims, the more fun they seem to be
However the thought of trying to work out what I need to do to correct it if it turn out black, more or less exposure would drive me crazy. I have enough problems trying to work out how to correct the meter reading when exposing against a white or black background.
I've never tried it but would be tempted to simply say "do what you wouldn't normally do"
Since it's a positive medium, you have to use reverse thinking. If "white" light hits a regular negative, it turns black. So, if the same "white" light hits a non negative emulsion (like the Ilford Direct Positive), it becomes white. Just like slide film and Polaroid.
So, using the same thought process, if the print is mostly black you need to add more "white light" (exactly the opposite of regular darkroom work). And if the print is white, you have to give it less exposure.