So on the usual multi-way flops I almost never C-bet unless I hit the flop well.

However, on the rare occasion that It goes heads-up into the flop, I am unsure whether or not to C-bet when I whiff the flop.

Against players I deem solid I will C-Bet more but vs calling stations/wildcards I will almost never C-bet

Is this correct? Should I be betting hands with little equity like backdoor straight draws or Backdoor flushes? (Vs bad players)

You want your opponents to make mistakes. If your opponents are calling without a hand then exploit that. For example.

Playing 1/2 and calling stating villain open limps with A9s. You raise to $12 with KQo and villain calls.

Flop is 842r and you c-bet $15. Villain as expected calls.

Turn T. You bet $35. Is villain really calling again? Well let's say that he does...

River is a 6. You push for $150. Even calling stations are folding without a pair here. Nice of him to put all that extra money in the pot without much of a hand. Yes sometimes he will wake up with AT instead of A9 and snap call the river but most of the time he is going to hold what calling stations usually hold... a mediocre hand.

There's going to be times in a multi way when it's advantageous to cbet. Think about what they're calling with...

Connected bwys, mid pockets, suited high cards...

Also what are the dynamics? Is it late at night? Is the table tilted? Is it a tournament near a bubble or break?

How do your opponents respond to cbets they hit or miss? do they station type? Do they raise? for value or as bluffs? Or all of the above?

Low paired rainbow flops: 233 722 JJ4 ... depending on dynamics you can even cbet the high gapped rainbows as well ... A72 K42 etc ... if they call ... and you narrow to down hu you can play some really good poker on the later streets

Are you saying that we exploit calling stations by bluffing with air?

Yes. And at the same time you also exploit them by value betting with hands weaker than your normally would. That sounds contradictory but it is not. Knowing your opponent and bet sizing is key here.