DC ADIZ procedures?

I'm planning a trip from HPN to GAI soon. I've read all the NOTAMs,
and all the other stuff AOPA and others have put out, and I'm still
baffled how this is all supposed to work. Some of the material
directly contradicts other stuff (AOPA's presentation says you MUST
close your ADIZ flight plan, stuff on the KGAI home page says you
don't have to close it, for example).

As far as I can figure out, all I need to do is call 1-800-WX-BRIEF
before I depart HPN and tell them I want to file an "ADIZ flight
plan". Then I get flight following and as long as I'm talking to
Potomic Approach I'm cool, right?

Same deal on the way out; I file with FSS, call Potomic Approach to
get a code before I take off, and that's it.

Am I missing anything?