What I was taking issue with is that you said you don't count on the last EV... you just keep battling.
I would highly suggest counting for even the last EV - when you get done, you'll go for an EV ribbon and she'll say "No" if you've done it right. Then you save the game, and go get 2 extra Evs and try again - 30 seconds work and it offers you two "checks" to see if you got it wrong - 1 to see if you got too many Evs (in 252/252/4 spread it means you probably went 255, which means start over), and 1 to see if you "missed" something somehow).
I've delt with several EVers, and too often than not they get it wrong 50% of the time or more. Your method sounds good - but the human ability to get miscount even under the most controlled of circumstances makes having a "check" invaluable.