I am totally lost with this maintaining closed shoulder with relaxed arm combo, I just can't do both at same time. Or, am I just way overthinking this stuff.
Assuming RHBH. Have an imaginary target. Stand with your shoulders pointing in a line to it. Step your left foot back so the toes of the left heel are about in line with the heel of the right foot.
Now move your right shoulder forward by about half a foot or more. Two ways to do this, either hunching the right shoulder forward or left shoulder swinging back, counter to the right going forward and turning from the hips (not waist, hips) . Do a bit of both ideally.
Dangle your arm as loose as it can possibly be from the shoulder. Voila. You've now got a closed shoulder with a loose arm.
The problem for most players is that when they shift their weight they shift into an open shoulder position by trying to throw hard (shoulders open early as they swing their weight from back to front and try to throw it all hard) .
Next step then is to get on your toes and shift your weight(not swing, shift is basically walking from foot to foot, your spine stays upright relative to the target line, it doesn't swing back and forth) from back foot to front foot. Maintain that closed shoulder until the weight has shifted.
That weight shift will automatically move the loose arm, if your body position is right (stacked and athletic and the shoulders still closed) you will feel your loose arm come first into the body and then swing out and away as it finds the way blocked by your still closed shoulder, much like the motion Brad describes trying to achieve.
This is where the majority of us here differ from Brad in that we say the body will set up the positions to allow the arm to swing. He believes you can trick the body into the correct positions by focusing on swinging the arm away.
I'm dubious that people on the internet will pick up his focus and do anything but strongarm with them as I can see so many ways to do his thing wrong. That's not to say it won't work, but I suspect you need someone with you who knows what they are doing to make it work properly. It's also not to say that it won't have some distance improvement for people that have so far not had a very good throw, that doesn't necessarily mean its the right building block to focus on.
One thing you find in the form journey is there are lots of dead ends after promising starts. The one constant that always makes you better is better balance. always. whatever you do better balance makes you better.
This forum has moved more and more to an idea of get as balanced and as athletic as you can be and the rest follows rather than trying to find some magic bullet to instant distance.
With that said the Closed Shoulder snap drill is still the best drill IMO for teaching a clean consistent Hit.
The king of driving with a closed shoulder Garrett Gurthie -
- but we've all remained extremely aware that we're all standing on the shoulders of Blake & Brad (and others) that started the conversations online over at DGCR. 
