Situations where we should c-r as bluffs:
1. OOP on dry flops (like T42r) vs. PFR who c-bets too much with any hand that has something like 20%
equity vs. his continuing range (overcards, BD FD, gutshots, etc.).
2. on the Turn with backdoor flush/combo draws when either a scare card hits or against a decent player who understands what the turn C-R represents.
Also I'm starting to like the idea of check-raising as PFR vs. people who float too much or robotically bet when checked to. Also, check-raise KK+ in 3-bet pots from the blinds.