Thanks for the kind words guys.
Njal, You are correct in that the "streaking Effects" can be used for streaking but why stop there? I thin them out and use them for washes, filters, etc. The reason I chose to use this color in the airbrush in this way was to tie the general dirty colors together from top to bottom. I don't think that Tamiya Buff was "intended" to be thinned out and used as a dust/dirt layer either but it sure works well!