/cgl/ - Cosplay & EGL

So I've never before done cosplay, but I want to paint a 3D printed prop. I've never done painting like this before (not miniatures, not cosplay, not in any other capacity).

Pic related is the prop (the skull).

The idea was sanding the 3d print to be smoother (and for color to stick), then priming it with spray paint and then painting it by hand with a brush.

Any good sources for tutorials on painting props/weathering them/adding texture?
I heard you should add a coat of clear spray paint between your color layers and the weathering color, is that true? What would you search for to get good tutorial? "paint 3d print" is too vague.