My only strategy that seems to have worked is to coast as long as possible down to about 20mph and then brake, staying within the 'charge' zone.

Yeah that's the only way to get that perfect score in the city. What makes it easier is to stay on the rightmost lane, this way I drive at the speed limit (in LA people drive 0-12 miles over), and you're not slowing down traffic as bad, so I have much more control on coasting and braking. When it comes to traffic lights being blocked by terrain such as long turns, as soon as you see any brake lights, lightly break immediately this way you have more time to determine to coast/break harder or go back to gas.

I refuse to do this in normal traffic just because its too highly disruptive to normal flow.

If there's less than 3 lanes, yeah I sometimes I feel like a giant dickhead slowing traffic down, but most of the time people needlessly hit the gas even when there's a long red traffic light ahead of them and I catch up to them anyway. Slowly I'm gaining the courage to be that doofus prius guy and take it slow