Your union bulletin board should have info on meetings. If you direct newbies to a few meetings and shake the BA's tree, you might start something.Part timers should get more involved. But part of the problem is that (at least in my hub) new hires especially don't even know about any of this stuff. I feel that the union should have some sort of "onboarding" process with the new hires. They should take some time and tell them a little bit about the contract, what they are and aren't entitled to, who to talk to if there's an issue. None of this was ever discussed with me. It wasn't even until a couple months ago that it was revealed to me that pre loaders are guaranteed at least 3.5 hours. So much of my first year I was hurried off the clock, being none the wiser that I could've gotten more work for that given day.
That might not be indicative of how all the locals inform new hires and such, but around here there's virtually no communication.