At what level of seniority should messaging be sounded out and then finally given the all clear for use?

From the start of a project, outline a clear RACI on the key deliverables needed to get to market, including 1) Positioning, 2) Pricing, 3) Messaging. Share it with the working team early, so you can make sure everyone is on the same page.

For example, positioning and pricing might require approval from a GM or whoever is accountable for the business goals, whereas messaging might require approval from a Senior Marketing Leader. Further defining the RACI helps you determine who has to approve the messaging versus who is informed or consulted. 

For the approver, share early thoughts as soon as you can and before you’re too far along in your thinking or in briefing in other teams. If that person is hard to find time with, I would try to find someone who they regularly touch base with and who can get you directional feedback. Assuming they don’t raise any red flags, share a document or deck with the decision-maker for formal approval, making it clear what the next steps are once you have their approval. For senior leaders, it’s often worth emphasizing the “why now?” for alignment and whether or not their approval is required to unblock other work.