One of the things I like about being a trainer, is the opportunity to share my knowledge and experience with colleagues.
The preparation for a course is a challenge in itself. It makes you take a really "deep dive"!
To be a good trainer, it is not enough to know how the technology is implemented or what the solution should be. You need to know all possible options and why this particular solution is the proper one.
Probably the most important things for a trainer are the experience gained through working on different projects, the ability to share your knowledge in simple terms, and the need to constantly update your skills.