I use HR monitoring to pace myself, making sure it not only doesn't get too high when I'm on the switchbacks, but also that it's in the appropriate range when I'm starting out so I don't set out too fast.
Everyone feels their best when starting out, leading to a tendency to go too fast, even though it doesn't feel like they're walking too fast for the conditions.
Another good technique to disciplining your pace is using the rest step. This is usually most beneficial on steep terrain, but if you sense you're jackrabbitting at times on any ascent it can reel you back in to a cadence you can maintain for quite a while without stopping.
Fortunately the main trail is so well graded that I can usually maintain a consistent pace, while stopping for rest about 10-15 minutes every hour. If my HR gets above a certain threshold then I'll just stop and wait for it to go down. Using an altimeter to measure pace also is useful, since I know I can handle about 100 feet of gain every 5 minutes or so at high altitude, as long as my HR stays within a certain comfort zone.
But yeah for steep and inconsistent terrain the rest step is definitely a good idea.
