I would like to see the average grade on that climb. Honestly if most of that grade is over 10 with sections as you say up to 15, well that's really steep. I would also assume there are switchbacks on a road like that. Braking on a very steep, very twisty road at 270 lbs...I would say find another hill to ride.
however if the road really isn't that steep, and it's not that twisty, I think everyone is going to agree that modulation is the key. I live in the mountains and can't go in any direction from my house for any real distance without getting 1000 feet of climbing. I try to ride sections that aren't as steep without braking, and brake harder with both brakes just prior to a corner, I then try to stay off the brakes as long as possible before going back on. I don't ride the brakes, I am either getting on them hard, or off them all together.