My experience with a pyro developer is limited to the one manufactured by Bergger. Full instructions can be found in this document. However, by carefully following these instructions, the first film I developed didn't look that great to me ...

The negative appeared flat and low in density. I therefore browsed the internet to get advice and I found out that the sensitivity of Bergger film are generally lower than declared and longer development times are suggested by users. Now my negatives look better but my feeling is that you have to experience by yourself the perfect mix for a successful pyro development!