Unfortunately, it's one of the hardest things for even the most accomplished leader to do effectively. Nevertheless, the higher you climb up the corporate ladder, the more critical this skill becomes. In fact, it's a requirement for executive management.
Fortunately, I learned a few techniques and tricks over decades of doing this sort of thing that I'm happy to pass along. And no, they don't teach this sort of thing in business school.
Define the process and ground rules
The "set up" is more critical than any aspect of any process. A CEO once told me that most business disagreements were due to conflicting assumptions. So, if you explain upfront how the process works, why you're doing it, what you expect from participants, and what's on the table and what isn't, you can eliminate a healthy percentage of unproductive churn.
For example, if it's a rebranding process, explain exactly what that means - that it's about changing positioning, not changing business or product strategy - and what it entails. Allow time to answer questions and get everyone on the same page. Of course, insights from one process can ripple through others, but that's for another time and place, right?
Make it "their" process, not "yours"
You may be the leader or facilitator, but everyone else in the room is there to express their views, debate, and make decisions. Design the process to include heavy participation so they feel as if it's their process and you're role is solely to help them reach consensus. That puts you in an authoritative position without you actually having to be heavy-handed.
In other words, if you appear to be pushing a viewpoint or perspective too vehemently, then your role as leader or facilitator is tainted. Senior managers and executives do not like to be told what to do, especially not by a peer or outsider. But if their voices are heard and there's ample participation and debate, then you can be more authoritative in driving alignment without appearing to be pushing an agenda.
For another perspective on this, check out Peter Bregman's How to Counter Resistence to Change.
Don't forget to close the deal
For some processes, it's wise and appropriate to bounce tentative conclusions off the next level of management or even outside analysts or consultants under nondisclosure. Bring the feedback to the process and then finalize. It's worth an extra iteration and lends weight and credibility to the process.
Don't laugh, but you'd be amazed how many executives lead an entire process over weeks of meetings and never close the deal. Until you finalize and document decisions, conclusions, and plans, you leave the door open for continued debate. Make sure you define success with appropriate goals and metrics.