The problem I think is that in a three way pot, odds are that someone has hit the flop. C-betting may backfire if someone hit trips, A and kicker for two pair or even both could call and give each other odds to chase. Any KT, QT, KQ, spade suited has the odds to chase. AJ, AK, AQ, JJ has you dominated and probably will call. If you are going to semi-bluff, bet the pot or 3/4 pot. Then if they call you know your beat. Just my opinion, but i'm just learning. someone will tell you where i'm wrong.