As I'm not sure of what effect Pyrocat has on a normally exposed neg, could I just suggest that if the neg is low-contrast-but-dense then you try a pre-flash. If that's the case, then experiment with different amounts of flash, flash only grade-five etc. Start with the most flash at the hardest grade, just to see if the results go in the right direction. It brings out texture and form in dense, sunlit backgrounds where you have a shaded subject and so on, so you may find it helps get a better separation on a denser than normal neg too (if it isn't completely uniform anyway).