Hi there, As a certified ChiRunning instructor, here is what I teach (this has also helped me a great deal personally). For most hills (gradual to moderate) lean into the hill, keep your feet under your center of mass, and allow your hips to rotate back with the hill as your stride goes out the back. Relax everything as much as possible and let the hill take you. If the hill is a steep one (one on which you don't feel safe leaning into), then a heel strike is really the only way to go- but it is not a highly impactful heel strike as in overstriding on the flat. Just lower your center of gravity, sit down on your sitz bones (bony protrusions that you sit on when in a chair)and let your quads help a bit. Take short, shuffling strides out in front of you, heels landing first. Hope that helps.

I don't claim to have answers, but when I run down hill I think about a couple of things. The first thing is to run with the hill, don't fight it. If you fight the hill, you will be inclined to use your heels to put on the brakes. Once you are running with the hill, grabbing at it like you would on the flat, you can use your quads to control your speed.