What are some ways to solidify a messaging shift with the field?

One way I've found some success in rolling out to the field is using one of my better reps as a champion of the new messaging and having the "pitch" for the new messaging come from them. Instead of it feeling like the messaging is coming from marketing or product, if you can arm one of the most respected sales persons with the new messaging and have them roll it out through a presentation or role play with the field it might resonate and be internalized better. Some other ways I've found success are making sure you're connecting it to a customer win or use case specifically. This can help people take more abstract concepts and understand how it applies within prospect or customer conversations.

Top-down won't work, don't force compliance. 

It has to be bottom-up, where the reps discover that this works. 

You can try SPIFs or internal competitions for the best sales calls. Some companies are using meeting recording products like Gong or Chorus that might help in this regard. 

As soon as you can get your best reps on the new messaging, that starts the chain reaction where the rest of the sales team follows. You'll need to iterate with these top reps' feedback to ensure they can be agile and nail it. 

A harder problem is if you are reaching totally new buyers. That isn't just new messaging, that is a pivot of the whole sales engine. It require reseting target account lists, strategy, even revaluating the reps in your company. That takes time.

Over the years I have collected and adapted a number of messaging tools. I have come up with a structured process for messaging development, and one of the deliverables is a source messaging document. Source messaging documents contain 50-, 100-, and 200-word descriptions, and usable snippets of text or approved slogans and tag lines. One of the core pieces is a matrix where we draw an oppositioin between "how we think" vs "how they think". This is useful for really internalizing what is different about us. Sales people get a lot of content thrown at them, but they really don't need that much content. What they really benefit from is messaging strategy, sales plays, and objection handling. All of that rests on how we think, act, do, build, or otherwise create product differently in comparison to the competition. So one suggestion might be to do a "think differently" brief to teach your differentiation at more of a DNA level. If its crisp and digestible, salespeople will internalize it and pivot better duriing sales conversations.