How to Implement Track-Based Development in Greenfield Projects

Greenfield and Legacy Wars would be using maybe Gitflow or some other branch base possibly in-house custom way of branch-based process. They may also have lots of manual testing, not a lot of automated testing. So how can this legacy or Brownfield projects, what can they do to move into the trunk-based development process but in an incremental way? There's some readiness things, right? We have to speak to the QA group and talk about shifting everyone from manual to automation skills.