For color contrast control masks I use FP4+ in TMax RS developer. Gives a nice neutral colored mask. I use a pin register system from Alistair Inglis. I use the same film and developer for the few unsharp masks I have made for black and white negatives too, just because I had the approximate process worked out.

I also use 4x5 film for both 4x5 and 120 masks. I have never made a mask for 35mm, so I don't know how well it works. If I were to do so I would cut the film down to save money.