I didn't down vote! I would say that the Buddha and the Buddha's system are not ways to reform people, they are ways for people to reform themselves.
What the Buddha did in cases like Angulimala was to perceive the particular approach which would be met with a comprehension that lead to their change or understanding of the goal. And this also usually under circumstances of compassion specific to the individual.
The idea of reforming people involves ambition, desire, wanting, etc. I think the distinction applies especially in cases such as prison reform. The lack of a specific target and certainty that one is providing an approach that will lead to attainment of the reform tells me that what is at work in a case like that is personal ambition rather than compassion.
When the Buddha speaks of the good man being of benefit to gods and men, he is speaking about the example they set. From the good example people reform themselves.
So, I suppose I would give as answer to this question: the best method for providing an opportunity for people to reform themselves is by being a good example.