The triple dumbbell press is a great way to stimulate hypertrophy and muscular endurance. You get that extra burn by changing the dynamics of the exercise and using your hips to assist with extra reps.
It's a combination of three different overhead press techniques. You might want to practice each technique with a lighter weight to build your confidence before hitting heavier weight.
Do these three exercises without rest in between:
The dumbbell strict press: Stand with your feet about hip-distance apart; keep your torso upright and your abs braced. Then bring the dumbbells up to your shoulders. Using only your arms and shoulders, take the dumbbells to an overhead position with elbows locked out. Keep it strict; don't allow any other body parts to help out.
The dumbbell push press: Using the same starting position, initiate the press from your hips. Load your hips by dipping down slightly, allow your knees to come forward, but keep your heels planted on the ground. Then drive the dumbbells up with the power of your hips and finish by locking out the movement with your arms. Avoid overextending your elbows by using more power than you need to from your hips.
The dumbbell push jerk: Using the same starting position and hip drive as before, you'll now catch the dumbbells overhead with bent legs. Instead of pushing up with the hips and finishing by pressing with your arms, load the hips, drive the dumbbells up, then dip into your hips a second time and catch with your arms fully extended. Return to standing before lowering the weight back down again.
Try to add some weight each session, or add a rep each time instead. It would look like this:
Week 1: 5 sets of 6
Week 2: 5 sets of 7
Week 3: 5 sets of 8
Week 4: 5 sets of 9
If you're more advanced, hit as many of each exercise as you can before you HAVE to change to the next one. You'll probably get three good sets like this, then when set 4 and 5 start getting ugly, extend your rest times.