Re:best way to use Masteron in a test/ deca cycle?
3ml isn't so bad as long as you're hitting a muscle large enough to take it.
But it sounds like you shouldn't need to shoot 3ml in one go:
Mast needs to be shot eod at a minimum IMO, so shooting with tren e would make some sense (if you can get tren e).
If you're sticking with the meds you outlined above I'd do this:
0.5ml deca eod
0.5ml test eod
0.5ml mast eod
A few more jabs but less volume in each shot so you could use pretty much any site you like. Nice even blood levels of all meds, both long and short esthers.