Every meeting, at the beginning of the meeting, everybody was required to complain for 5 minutes. Just talk about all the stupid decisions that got us to this point, how unreasonable the timeline was, any staffing issues you were having, any parts you needed, etc. 5 minutes. You are required to complain.
It helped a LOT, and almost a decade later when I interact with that team, we still all look back glowingly on that practice as something good.
It was a tense project, and that "you have to complain for 5 minutes" completely broke all of the tension, and let us all work together effectively. If we hadn't implemented that policy, we might not have finished the project on time.