Simple Green or US version of Windowlene (still has 5% Ammonia in it) should shift Vallejo.
As above, it takes time to get the hang of Acrylics, my thoghts so far:
VJ POLYEURETHANE Primers behave differently, need a higher pressure & shouldn't be thinned, though I do....
I thin with a few drops of Original FUTURE, (1-3 drops future to 8-10 VJ) makes it more workable, 'hardens' it to handling & allows a little bit of re-work sanding/corrections.
VJ do a decent range of primers in armour colours, my faves are the OD & British Bronze green, saves a painting step or to.
VJ often/always needs a decent primer undercoat.
Mix VJ very well, I add a few 3-5mm stainless steel nuts (waay cheaper than stainless bearings)
Thin slightly with the new VJ or Ultimate thinners (test outside the airbrush in a disposable cup, NEVER IPA, Tamiya X20 or Lacquer... ) if you have the old thick white gloopy VJ thinner bin it, not much use for airbrushing.
Use a little Airbrush Flow Improver 72.262
Vary your headset. After I dropped my Iwata CS on the floor & had it serviced, (!)
I switched to a 0.3mm headset from the fitted 0.5mm & found it a lot easier.
Finally your environment matters, get your air clean, pref using tank supplied air & moisture traps and Local humidity will make a difference, 100% dry Arizona will be different to 100% humid Alaskan...