The militia, in the 18th century sense of the word, is not something that is created. It exists at all times in the form of armed, competent, able bodied citizens living in society, but who have the potential to defend their land in time of crisis. That's why those unable to bear arms responsibly (children, the mentally unsound, criminals) don't bear arms legally. Remember,
A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
This means that in order to defend the security of a free state, there must be pool of competent (well regulated), suitably armed (not be infringed) and able bodied citizens (the militia).
So, there is no reason why the government couldn't require training for firearm ownership, and if you want to get technical, there is good reason why it should.
Actually, there is a good reason why the government should NOT require training for gun ownership. You cannot secure a FREE STATE while simultaneously allowing the government to dictate the criteria for gun ownership, for the government is the antonym of freedom. The second amendment is there to protect the people from the government - it is the ultimate check to maintain the balance of power.
As we witness the actions of the Obama administration and the democRATS (and some Republicans) in general, its purpose is becoming very clear.
You have a couple of extra commas in your version of the Second Amendment. The Second Amendment reads:
A well regulated Militia being necessary to the security of a free State, the right of the people to keep and bear Arms shall not be infringed.
http://web.archive.org/web/20070630135433/http://www.freerepublic.com/forum/a39388c210c1b.htm
If the government can impose training requirements in order to exercise the right to keep and bear arms, it can eliminate the right by making the training requirements extremely difficult. That is why training may not be required.