Yan 

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.