Mold making help

I have a positive cardboard model that I want to make a negative fibreglass mold from. I made it out of cardboard to get an idea of how I want to make a styrofoam model, but it turns out I made the cardboard version perfect and there's no way I'm going to be able to transfer the design onto styrofoam.
So I was wondering if there is anything that I can put onto the cardboard, a spray or a wax or something, that will smooth it out and give me a nice surface to work with?
Or, does anybody know of any modelling forums where someone could answer this question?
Thanks.