I normally side with db and Cindy, but they're leading you down a dark path with a dim light.
1st, you need to determine what is the goal of the audit, the topics that must be included in training to help develop the competence to achieve the goal , and how much training is necessary.
2nd, you better make sure that any trainer you use is competent in the subject matter themselves and is actually capable of delivering the material as required.
3rd, you need to determine how to assess the effectiveness of your training.
There are some things to remember regardless of the type of management system auditor we're looking at...this actually goes for everyone within a "system".
1) Roles, responsibilities and authorties must be defined.
2) Training needs to accomplish #1 must be determined
3) Programs to accomplish training needs must be developed
4) Methodology to assess or determine the effectiveness of training must be developed
5) The trainers need to have 1-4 applied to them too.
You want to develop your auditors? Get a copy of ISO 19011 and refer to Clause 7. Change the should's to shall's and then do them.