Learning to relax is obviously a useful strategy for dealing with unwanted anger. There are lots of ways to relax, though (see here for examples of mediation, deep breathing, and taking timeouts). One of the best is to use visual imagery where you visualize a relaxing experience from your memory or your imagination (a trip the the beach, a hike in the woods, etc.).
In fact, if you’re not good at coming up with visualizations on your own, you can even find a few websites with free visualization scrips for you to practice with (see here for an example).