How far do you go?

I learned a bit too late that a typical fleshborer on a typical termagant is basically impossible to paint completely if one assembles the entire model first. This, of course, is often true of many 40k models, but the box always shows the model being assembled first.

So now I'm at the stage in my army creation where vehicles and heavy support must be addressed. In my Nid army, it was simple since the MCs are essentially big versions of the scoring units. But rhinos, predators, dreads and defilers? What a collections of inaccessible areas and fiddly parts! So with the defiler that I'm putting together now, I've stopped at a fairly logical point for priming:

The legs are not glued to the chassis. Any further assembly would seriously impede the application of primer and paint.

Do any of you actually prime/paint after completely building something like this?