Following approaches can be used but that will vary based on the actual project scenarios or from organization to organization

Stage 1:

For any DevOps implementation, and assessment of the existing process and implementation for around 2 to 3 weeks taking an average of 5 applications is a must to gauge the AS-IS process, identifies the improvement areas and provides a roadmap for the implementation.

Typically a senior profile like a DevOps architect should be involved to conduct this assessment.

Stage 2:

A pilot POC can be done to showcase the end to end working of DevOps. Once this has been accepted and approved by the end-users only then the actual implementation, handover and rolls out the plan for the projects involved should be carried out.

Any pieces of training required will also need to be imparted to the process or tools. DevOps architects, engineers, and testers would need to be involved at this stage.

Stage 3:

The projects should now be in DevOps mode with all the components of continuous integration/delivery/testing and monitoring that is being followed.