Dear …
I want to personally thank you for the __(type)__ training you provided to our __(type of staff)__ staff on __(date(s)__. You did a commendable job. It was both enjoyable and informative. You captured the interest of the all participants very well and your expertise definitely shone through as you delivered the course material.
We received very positive comments from those who attended your course. They really enjoyed it and found the information to be quite valuable. Once again, thank you. Your solid knowledge of the course material and your ability to convey it to your students is most commendable.
Sincerely,