With acrylics I'd prime, especially if you are going to mask over it. Tamiya white or grey rattle can is good. I just give it a light scuff with a grey scotchbrite pad. You can get one at any auto parts/paint store.
Helps to avoid any peeling when unmasking
Vallejo takes a couple of days to harden up, so don't rush it.
I find that the MM and Vallejo gloss dark sea blue is more of an"angry sea green" , with a slight blue tinge. Don't know how accurate that would be as most color pics and film show a real blue color. But have to take into account film and print.
With Vallejo I'd stick with their thinner and flow improver. The model air line is supposed to be ready to spray, but some thin it a tick more. Depends on how your brush works with it. You can pop the spout on the bottle and stir to mix way better than shaking and rolling the bottle