I know this post is old but I saved it so I could come back when I had time to respond.
A quarter to a half inch is added to the side the man "dresses". That means a quarter inch is added to the front crotch seam on the side his penis lies. The front seam is then eased together. If he dresses center, then there's no single-side pattern adjustment.
A small reinforcement panel is added to the front crotch points for protection from sweat and stretching. You can use self fabric or Silesia pocketing for the panel. I don't have any photos unfortunately, but it is addressed in Cabrera's Classic Tailoring Techniques, which I highly recommend in your library if you're getting into menswear. There are lots of pointers on pressing jackets, fit issues, and even some patterns that will be helpful.