When to bluff small pairs on flush draw flops
There is a right way and a wrong way to turn a small pair into a bluff when there are draws on the flop.

Small pocket pairs are used as occasional bluffs on flops with high connected boards.
If the board is something like J♥9♥7♦ we might bluff with pocket fours, for example.
A hand like 44 is very happy to get folds on boards like this and once-in-a-while can win unimproved against a flush draw.
When we do bluff a hand like 44, make sure it is specifically 4♦4♥ - the two suits on the flop.
Choosing the right bluffing combos

This is not for the backdoor outs, we are not trying to hit runner-runner to make a heart flush with our 4♥ - good luck with that.
The reason is that if we bluff, get called, and then hit our set, we hit a clean out.
If we bluff with 4♦4♥ and turn a set, it will be a 4♣ or 4♠, which does not complete a flush.
If we have another combination of 44 and the 4♥ gives us a set, we could be in for a world of pain. If it is the 4♦, we have also brought a 2nd flush draw into the mix.
Small pairs should only be occasional bluffs in these spots anyway, but when we do bluff, we want to make our opponents make a flush less likely, especially when we hit our miracle set.
You can get Dara's free book on effective poker study by joining his mailing list.