I don’t think it’s a good idea to use X-20A, Tamiya are closer to a lacquer than to acrylic, despite being labelled as such.
I have used Vallejo Airbrush thinner:
And water should work, despite not as good.
In any case, a primer helps. And do not spray too much paint, pull the trigger slowly and paint using several light layers until it is covered -if you try to cover at once, it will hardly work.
Yes, you need to use a water based acrylic thinner like their own brand. Windsor and Newton acrylic flow improver works really well with it too.
Tamiya and Gunze thinner won’t play ball with Vallejo, Revell or any other type of acrylic.