Looking good Geo.
When spraying gloss paint onto relatively shiny plastic, it's best to have a thin primer coat, especially with black, red and yellow. A light coat of a mid grey colour will do the job, and will also help you to see the paint coverage easier.
It doesn't have to be a perfectly opaque coverage, as long as it's relatively even, to allow the gloss to 'key'.
Always spray gloss paints lightly, keeping the airbrush moving, building the colour in two or more coats, allowing some drying time between coats - it doesn't have to be fully dry, but avoid 'going over' the same area(s) too soon, as that how pooling and runs occur.