have you ever used trimming powder? It helps good stripping. I have very good experience with Bio Groom Harsh Coat Powder. SChnauzers in Europe must have WIRE otherway they don't win So we train a lot trimming and stripping
I know that blacks are not so popular Overseas. They are very popular in Europe. We try to mix European a NA bloodlines here for good results - harsh coat but huge legs furnishings.
I think that of p/s coat is more dificult then black coat. Our dogs have only one colour and you needn't care of good colour dixtribution like at p/s.... Black is black
We strip our blacks about twice a year (back and head too) and then they show themselves in one coat. One my fiend from Australia has sent me HOrse Block which helps trimming of the longest hair - very useful tool.