The training companies provide are nothing extraordinary. Usually few days of managerial training spread over few months on what you can and cannot say/question employees i.e. religion, race etc. and few other tidbits on general managerial operations. If your boss is too lazy to send you to one your HR must. It is their obligation.
However that is not the crust of being a good manager. Emotional Intelligence (EQ) and having Empathy is. Realizing that every person is an individual and as such should be treated individually. I recommend books by Dr Paul Ekman like Emotions Revealed & on body language by Joe Navarro that will give you a head jump in working with & understanding people.
Unfortunately, the mistakes a novice manager can make - hiring the wrong people, irritating good developers to the point where they quit the company, etc. - are much harder and more costly to clean up than the kinds of mistakes you can make as a developer. For one thing, there's a multiplier effect: your actions suddenly affect more people.