We have a set of curricula that I have developed that we use for both training new volunteers and hosting workshops to the public: https://docs.google.com/a/communitycycles.org/document/d/1FN0MHz1JshRDgG-vTpXwgPjTY9k7HI_hLXj8P0F7IlM/edit
This was mostly developed by me, so it is not as robust or validated as the Park Tool School or Barnett's, but it serves us well. Bikes not Bombs also has a pretty good curriculum but for their particular program.
It is not unfair to ask for monetary compensation or a volunteer requirement. We typically ask that volunteers commit to 3 hours per week, but have not currently turned anyone away from the classes. People wanting to learn bike mechanics are the low-hanging fruit for recruitment, so it makes sense to build their skills.
Lessons to be learned:
- training does not make master mechanics out of novices overnight
- "advanced mechanics" who have worked from their home do not necessarily know the proper tools/techniques for doing mechanics