An external consultancy can help an organisation progress in a number of ways. When not outsourcing, these usually fall into three categories; training (someone shows you what to do, in a controlled environment), mentoring (someone shows you what to do, in your own environment) and coaching (someone encourages you to explore and develop your own environment)
Training is usually fairly low cost, but it usually only provides an overview of what something can do for your team. Training can be a useful morale boost, but it very rarely becomes immediately applicable to your business domain. Acquiring a new skill requires practice in a real environment. This loosely corresponds to moving someone onto the Dreyfus skills ladder or moving from Unconscious Incompetence to Conscious Incompetence in the four stage model.
Mentoring allows your team to try out new skills under the guidance of a skilled practitioner. When the team member does something inconsistent with current practices, the mentor will intervene, explaining why they are intervening, any likely problems from the original solution and demonstrate an alternative solution, explaining why they think this may be more appropriate. After the discussion, the pair may decide to continue with the original solution and see if it works, or go with the alternative. This loosely corresponds to moving the team member to Competent on the Dreyfus model or to Conscious Competence in the four stage model.
Coaching is a more hands-off approach. The team will continue to work in their normal style, while the coach observes. Using Socratic questioning, the coach will generally guide the team members to explore new avenues of thought, to discover problems that they are likely to encounter and to work in a way that minimises the likelihood of any unknown issues encountered becoming an insurmountable block. Coaching offers the highest value, as it gives the team a toolset for modifying their thinking on an ongoing basis. It corresponds loosely to moving into the advanced stages of the Dreyfus model (Proficient / Expert) or towards Unconscious Competence in the four stage model.