EdGrune - thanks for the info... I will try that (or similar), and see how the top gray layer looks over the red one (better than a red over gray I think!)
CG Bob - Yes, I did a search in here, got lots of info about the various shades of green (Dark, Tropical, Forest) people use for the PT boat... this "plastic" green was just painful to look at, and would have been difficult (at least to me as a non-expert!) to paint green on green and see any nuances...
I will also try to simply prime light gray testors enamel as usual, very light coat.. then AB more coats as a "final color", maybe add a tad darker spots to give it an uneven look, as suggested... thanks again!