I usually go a little closer to the body than 45 degrees. I usually don't use barbells for pushing due to getting my left arm destroyed in a car crash, but I find that they don't aggravate my shoulders as much when I do my CGBP on slight to moderate incline.
I'll second what others have said about close grip quickly building up close to your regular grip max. I remember Dave Tate and Louis Simmons both saying to always start with a closer grip, even for regular bench work, because you can always widen your grip and recruit a little more pec as your triceps start to go. It's been true in my experience.