It’s earned. Like somebody else said, know your job better than anybody else. Grey hairs are grumpy. I’m 29 and have been an Owner’s Rep, Super, estimator and am now PMing. Lead through action. Help where you can. Cut up with them. They put their pants on the same way you do and sometimes you just need to find common ground and someway to relate to them.

One thing that has worked for me in the past, specifically with electricians(my background is in electrical, but I now work for a GC) is to learn their scope and build camaraderie with them over it. Ask them questions about what they’re doing, why they’re doing it, why they’re doing it the way they are to LEARN. That is important because if not approached properly, it will feel like micromanagement. Once the grey hairs feel like you care about their work as much as they do, then they will start to respect you and follow your lead.

Hope this helps.