The DevOps service provider that you hire should have at least five years experience with automation tools such as Puppet, Ansible, Chef, and SaltStack as well as a high level of proficiency with Python, Ruby, PHP, and Java. They should also be familiar with continuous integration tools Jenkins, CruiseControl, CruiseCrontrol.NET just to name a few. It will also be tremendously helpful is they have experience deploying code, database management, system design and experience in software architecture.
When interviewing candidates, be sure to ask if they have any project management, risk management or Scrum Master certifications or at least some experience in these fields. It is not important where the service provider is located since the one that best fits your specific needs may not be in the same city, state or even country.
It will be necessary for the DevOps consultant to travel to your site location anyway in order to observe and study processes and provide a recommendation on how to fix them and in today's world it is possible to travel from point A to B in a relatively short amount of time and on budget.
While the service provider does not need to have experience in your particular business area, they should very clearly understand that the business needs of your company and technological changes need to go hand in hand. Everything they do must be based on sound business principles. Be sure to discuss all business outcomes that you would like to see as a result of DevOps implementation before discussing any procedural changes.
While the demands for DevOps consultant are extremely rigorous, the demands for your engineers are not much lighter. They should have strong automation expertise, capable of designing the building and operating a software stack and an expert skill level in either Docker, Chef, Puppet, Jenkins, MongoDB which will all be project-specific. Just like with DevOps consultants, engineers need to have soft skills as well. This includes empathy, communication skills, integrity and a desire to continuously improve and develop their skills.