If you do all your comic work on Photoshop, if you haven't already, use paths/pen tool. It will make your life infinitely easier when it comes to perspective (and fun! Maybe.).
Yeah, I use it a lot. It's frustrating making and stroking paths for every damn line, though. Sai's line tools are a little quicker for me.
Oh no, not for stroking paths (although that is kind of helpful). I just use the paths as guidelines, to set up the guidelines to the vanishing point. Since Paths are on its own layers, I can make two path layers, one to set up guidelines that I can delete later, and the other for the actual strokes. Makes things a lot faster.
You don't have to go to that much trouble to draw guides. Just draw or import a simple grid and use the transform tools to map it in the proper perspective.
Personally, it takes all but 2 minutes to set up the guides. :X It might not be for everyone, but I find it easier to work with custom-made paths just for the scene rather than trying to warp a guide to fit your sketch.