For the 30/30 DB Push Press does one work for 30 seconds performing Push Presses and then “rest” in a static hold overhead for 30 seconds, repeating this cycle 4 times?
You have understood the 30/30 Push Press correctly. There are a few tricks to make it easier on yourself but nothing significant. I used 10-pound DBs my first time through it. In fact, I developed it as a shoulder rehab exercise: I could press heavier DBs but I could not stabilize them overhead due to a shoulder injury so I had to figure out a way to make lighter DBs "meaningful". I knew that practicing 360-degree stabilization in a fatigued state is helpful for overall shoulder girdle integrity because static holds in the Forward Leaning Rest (top of a Push-up) position on the rings had proven it. My first time through my shoulder was twitching involuntarily by the end and I could not hold up DB up with my weak arm through the 4th round. There had to be a penalty for letting it fall, otherwise why not just “rest as needed”? The penalty for falling out of the rest is another round for every infraction (though we do allow lighter DBs to be used). James did a penalty round on Sunday after failing to make it through with 30# DBs. So, we say, “rest as much as you want during the ‘work’ interval – because it simply lowers the ‘score’ – but maintain the static hold as sacred since that’s where the real work is being done anyway.”
We always do the 30/30 Push Press during the seminars to teach a variety of ideas: to show that the legs should do the pressing because the shoulders must be preserved for the “resting”, to prove that just because one can drive a big weight overhead doesn’t mean the same load can be stabilized there, that 360-degree stabilization is more difficult than 180-degree (front-to-back) stabilization, that energy management is an important consideration, and that the if only light weights are available (in a hotel fitness center for example) one can “make them heavier” and do some effective work.
We also use the 30/30 interval structure with some other movements but the Push Press is the most "eye-opening" of them.
To improve “performance” with this exercise reduce the load but maintain the interval structure and duration. One could also reduce the load further and increase the length to six minutes. Less than four minutes though isn’t long enough to cause significant stress.
For the Push Press the guidelines that indicate when to increase or decrease the weight are these:
<60 total reps means reduce the weight for the next session
70-90 total reps means maintain the weight
>100 total reps means increase the weight
Don't take a single performance as a decisive cue instead watch the trend.
Other remedies for shoulder instability or weakness are overhead carries, which are tough because they include movement instead of standing still. Turkish Get-ups are quite good as well.