My own experience with this blasted achiev is that, at first, I tried doing the achieve by being nice and playing as well as I could (i.e., as well as a noob PvPer, in full PvE spec and gear, could do), and didn't get a single part of it on the first day I tried.

The next day I made myself into the biggest nuisance imaginable to my own team, refusing to do anything to help the team unless it gave me part of the achievement, and even intentionally hampering their efforts if it made easier for me to get something done, and got it in less than two hours for each of the two characters I was playing. Hint: bubbled players can't capture.

If I was doing it again this year, guess how I would try to do it.

BTW, as a side effect, this achiev alone got me so burned out with BGs, and PvP in general, that I refused to set foot on a BG again, except to farm achievements - and when farming achievements, teamwork be damned, I was not there to win, just to get an achiev done and /afk as soon as I got it (or go explore the BG as soon as I couldn't progress with the achiev anymore, while waiting for it to end - AV was really nice to stroll around).