Looks nice Doogs. The allies need the help. Your idea about pre-shading black, and then using a black-gray sounds good. That is what I was thinking of trying with my P-70. Did you read the Night Stuka article last year in FSM? That guy even mixed in blue in his black mix.
Did you come down to Modelfiesta? There were some pretty awesome deals, and some great entries.
Cheers,
Greg