I can't really say, since I find that we have a pretty homogenic team on this matter here at my work. We almost all have our curated lists of news to keep up on latest techs and trends, and even the ones who don't have such lists listen to those who have every time we share informations on our dedicated Slack channel. Appart from that, I'd say comunicating is the key. Share, write, speak. Enthousiasm is usually the best thing to keep everyone on track.

I know, I just get confused everytime I have to use it, and every time I see it in tests. Most of the time I get the answers wrong on this subject. I can answer pretty much everything else, I got good grades, and good results with my devs, everything is working fine. Except reference.

I have to admit, I'm still junior, but the thing that gave me most problems and still gives me some is the passage by reference. I code mostly (almost exclusively) in PHP, and this concept is really the dumbest thing that gives me proble. I mean like "some vars are passed by reference by default, some aren't, but you can add & before some to force passing by reference" bla bla bla. So in the end, I avoid using passing by reference and find other solutions.

Can't speak for anyone but myself, but as a Junior, I have to concur. I recently joined a new job and got sent to a client, primarily for ticketting, until I was given a project to work on from scratch. I have to say, the codebase was quite big and most of all needlessly complex, and I had to take three days just to get a quick grasp at the code section on which I had to work (a single Symfony bundle with dependencies). The ticket itself took me barely half a day to resolve. So basically I'd say it depends on factors such as the project, complexity of codebase, the amount of time you can spare to show him/her the code and answer his/her questions, and such. It also depends on the estimated time you will gain once this new person will be effective. So if you truly are in a hurry, and a big one, I'd say it's not worth it.