Role modelling is the best way. I just share honestly as I can on any given day. I notice that longtimers often respond authentically, and really are very reassuring to me. I certainly appreciate it, anyway.
I'm guessing that this group doesn't know one another much beyond the meetings. Another action step is to start fellowship activities outside the group. Start a coffee bunch. As trust builds, people get real.
What's very sad to me is when people settle for less than that.