Jorge,
I began with the shadow mask by contact printing lith film with my camera negative to gain a shadow interpositive. I then took the shadow interpositive and created a shadow negative. I then took two of my shadow interpositives to gain density and contact printed those and the camera negative and a sheet of unexposed film in register to attempt the midtone value interpositive (since the midtone densities are lower then my highlight densities) but I ran into problems here since my highlight densities were too near my midtone densities. This is where I need to come up with a way to separate my midtone from highlight densities. Since the midtones will print through before highlights. I hope that I am making myself clear here. Any ideas on how to do that?

To answer your questions about using a long scale paper like Azo...While Azo is incredible, this technique will allow controls over print local contrasts and values that Azo will not. Printing with Azo, in my experience, allows limited means of print manipulation. It does offset some of this lack of control by the increased length of tonal scale.