I believe this was from Roy Suenaka's article:
Pic as posted above by Jason
My own experiences with kote-gaeshi are that even with proper technique, relying on the wrist turn alone is insufficient especially those with conditioned wrists (not just Aikido but those in jujitsu and BJJ) can resist.
The way that I find works for me is to ensure that the opponent is overextended so that his balance is broken already before applying the kote-gaeshi so that you aren't just relying on the wrist-turn (and is generally less painful). Trying to kote-gaeshi someone with a strong wrist in a balanced position is risky. Just my 2 cents.