Engien braking is always a bad idea extra rpms and no real added fuel = not good, i may not be a mechanic, but there are reasons for not doing it, brakes and rotors are cheaper then engines. As far as dumping it from d3 to four, it really wears a tranny out. I've been manually shifting my tranny for a little over a year, but just to d3, never any lower. I know it has taken a toll to the poor car, but it keeps going solid. The fact is it is something that shouldn't be done often.
As far as starting in d1, and shifting your way up, I do have a differnet opinion on that. But how often are you goign to find a good race in an automatic withut Forced Induction, or something extra in it to make it really go. I jsut don't find it fun at all to race a grandmother in an SUV or a giant boat and loose. I do like bracket racing though, the auto is more consistant provided you don't touch it and leave it in d3 when you run.