You'll need to completly remove any odor of his previous spraying, as he will return to those spots. (You may have to keep him confined to one small area while doing this [such as a bathroom or utility room].) I have several resources for how do do this, including links to companies that sell the enzymatic cleaners needed for this task, under "Cleaning Messes" in the sidebar links.
Once you've removed all traces of urine odor in the house, get a bottle of "Feliway," which is a pherome-based spray product. It mimics the phermomes that cats use to mark their territory, and makes them less inclined to spray, and is rated highly. You simply spray it on his favorite "marking" surfaces, and because it's considered a "friendly pherome," he'll leave that area alone. Feliway also comes in a Plug-In that will treat a whole room. See my review for that product in the sidebar.