Consider x-ray duplicating film. It is a reversal film with simple chemistry. Enlarge as you would be making a print on paper except have the negative in the negative carrier with the emulsion up (not facing the easel). The film is very slow so even at full aperture opening exposures will be long. Also the opposite is done when burning or dodging ie if the end product contact print is to be "darker" the negative you are making needs more exposure. Like transparency film over exposure yields a "lighter" slide. The film itself has super fine grain so the grain if noticeable will be from the original film. Kodak has 8x10 and the chemistry is GBX. I believe Agfa still has some different sizes and also works with the GBX chemistry. The whole technique is very easy. I have been using it for pt/pd printing for years with excellent results. The learning curve would be to determine the exposure necessary to achieve the density needed for your final process.