I recommend the following practices when it comes to using ProtoPaint:
Clean all surfaces with soap and water let air dry
Prime all surfaces with primer #330003 (Note: For best results, the primer works best if you add a few drops of the base colour you will be using on you model)
Airbrush should be used with a #2 needle and tip to avoid "spitting and clogging"
Air Pressure should be between 20-25 PSI. If using lower air pressure, reducer #330004 should be used.
Paint will set up in 1 hr. But it is recommended to wait 24hrs. before masking and applying a second colour.
Avoid applying heavy coats. It is better to apply several light coats to avoid runs in the paint
Paint will dry to a glossy, decal-ready surface.
After decals have been applied seal them with flat finish #330005
Clean up your airbrush with soap and hot water.
After watching several YouTube videos this one best matches my way of painting...