against 3 other players, your pot equity edge is large. so for every bet and raise put into the pot, you show a profit in the long run. so the flop c/r is for value.

that being said there are still two more ppl to act after you, and if you miss on the turn (and check) they will likely bet because you showed weakness. but if you are in last position your raise probably bought you a free card.

i these situations i like to wait until the turn to raise. if i hit my flush then i c/r the turn (if im sure MP will bet again) and if i miss c/c.

so OOP i wait to raise and see if i hit. in last position i tend to bet/raise the flop.