In general playing for value (depending on how light they call, you can value bet lighter), but you can still
bluff players like this. You just have to understand how their ranges change and our cbetting tactics should vary against them.
For example cbetting the 368 board, they may peel
more with overcards and ace high than with pairs, and that makes barreling overcard turns less attractive, and barreling brick turns like another 6 or a 2 etc
more attractive. Just make sure your read of them peeling
lots with overcards is correct.
It can actually be good if you know they call lots of flop bets but give up tons on the turn. It's like someone who limp-calls lots preflop, but folds like %80 to cbets; you'd be isolating and cbetting them all day.
Also, don't think in terms of:
By loose I mean the type of player who has a 30% fold to c-bet and whos much more likely to have hit board we would normally consider dry.
...it's just silly. It's like saying "oh no, I can't cbet this flop, this guy could have
anything!". Thing is, he's
more likely to have missed most flops. I did a flop texture analysis thing a while back which can definitely be taken further, and I'd suggest trying this type of stuff yourself to see how various ranges hit various flops:
https://www.cardschat.com/forum/cash-game-hand-analysis-50/pokerazor-analysis-1-kq-3bet-pot-136958/
https://www.cardschat.com/forum/cash-games-11/pokerazor-analysis-2-cbetting-against-loose-137844/
Basically my point is that there's still room for
bluffing loose passives postflop, but you just have to understand what their ranges are like on different flop textures, and how it changes on various turns too.