I asked this a few weeks ago. Also ended up searching the Extract Brewing forum and the General Discussion forum keying in on "orange" and "zest". You will be able to find a lot of useful information if you read around.
I ended up adding zest at flame-out, by using a peeler to get larger zest peels making sure not to get any of the white portion (bitter tasting). This beer is still aging and won't be ready until March, will give feedback then. Good luck on your search. Cheers!