It makes absolutely no difference whether your pulse your brakes or apply light continuous pressure. As far as heating up your rims, the only thing that matters is your speed of descent. At the top of the hill you have a fixed amount of gravitational potential energy. By the time you reach the bottom of the hill you have a fixed lower amount of gravitational potential energy. During your descent that stored energy was converted to heat via friction. The conversion can happen in one of two ways: via air friction or brake friction.
If you bomb the hill at high speed and barely use your brakes, all that energy is converted by air friction and your brakes stay cool. Air resistance is the square of the speed, so the faster your bomb the hill the exponentially greater the air friction. If you use your brakes, the energy is converted to heat in your brakes, so they heat up. If you do this for long enough your brakes will overheat. However don't forget your rims are being continuously cooled by the air. The faster you're moving, the more cooling is taking place. The hotter your rims, the faster they transfer heat to the air. On the other hand if you descend like a grandma and take an hour to get to the bottom of the hill, you've spent so long converting your energy that your rims cooled themselves the whole time.
You can take the above and plot a graph. High average descent speed results in cool brakes. Low average descent speed results in cool brakes. Medium average descent speed results in hot brakes.
What you do in the mean time doesn't make any difference whatsoever. Apply the brakes continuously lightly, pulse it every one second, pulse it every five seconds. Alternate between front and rear. Use both at the same time all the time. As long as your speed stays the same it doesn't matter. When people say they pulse the brakes, what they're really doing is increasing their average speed. They're bombing down the hill, slowing occasionally so they don't die. Higher average speed = cooler rims.
This is how to descend properly: use both brakes to take advantage of maximum thermal mass, descend at a pace you are comfortable with. Listen to your brakes. When the braking sound changes, it's a sign the pads are overheating and their physical properties are changing. At that point consider stopping and taking a photo break. I have no scientific proof to support my method. However I did do a bunch of expedition touring in the Himalayas and on the Tibetan plateau so I've gone down a hill or two in my life.
Having blown a few tires off a tandem, I think you oversimplify the issues and therefore the method. What you're trying to do primarily is not blow the tires off. That's not good. IME if you work toward that goal, the brake pads will be fine. As you say, a hot rim will transfer heat more quickly into the atmosphere.
Tire pressures can certainly increase to the point where they considerably exceed the max allowable pressure, otherwise they wouldn't blow off. If one accepts that the goal is to minimize the amount of heat transferred to the air in the tire, then pulsing the brakes is obviously the way to go. When the brakes are off, the rim can cool. When the brakes are on, it can't. So the thing to do is to let the bike run as much as possible and then hit the brakes hard before corners. If it's a twisty descent, one alternates front and rear. The idea is to briefly hit the surface of the rim and then allow that heat to dissipate into the atmosphere as much as possible before heating the rim surface again. This helps to prevent the transfer of that heat into the bead and then into the air.
I run TPU tubes on my single, but probably wouldn't on our tandem. I've experimented with latex on it, but have come back to butyl.
It's not just rim brake bikes. Disc brakes can also overheat from the constant application of the pads, though that has nothing to do with this thread.
From the above one can see that one's best defense against overheating tires is to use deep section alu rims. The greater surface area allows faster heat dissipation. Again, the main reason to pulse the brakes is to allow aero drag to generate more heat, plus to some extent the quick temporary heating of the rim transfers the heat of braking more into the atmosphere than into the tire.