Here is a quick tip for dealing with complex 3 point perspective, without having to draw a million perspective lines. It's a technique I came accross after seeing it used by Craig Mullins on some Final Fantasy matte paintings, and Yannick Dussault on his personal project Hangar 7
It's very simple: using any 3D package, including free ones such as Wings 3D or Blender, simply create a very simple model of your scene with the most important elements blocked in and use it as a perspective template.
Not only will this enable you to create very accurate 3 point perspective without too much fuss, it also lets you experiment freely with composition and field-of-view as you set up your camera and move it around. You can also do a rough of your lighting setup too, which can also be useful for visualisation purposes.
Here's an example of this technique in action on the Lullaby Leslie painting:
And the finished image painted on top:
As you can see, I didn't stick to it all that literally, and still changed my mind about the composition later on, to bring the bed closer to the viewer, but it was still a very useful foundation on which to base the painting.