There's been a lot written lately about how Democrats are going to have to start working out details about single payer if they're serious about running on it. Now, we're getting a better idea of how Bernie Sanders will address some of them — though not all of them — in the "Medicare for all" bill he hopes to introduce next month.

The bottom line: It will give some basics on how to handle one of the main practical issues: how to manage a transition to the new system, according to aides. But don't expect a detailed explanation of how to pay for it, which of course is one of the biggest questions everyone will ask. And no, private insurance companies wouldn't have much of a role to play.

Here are some of the practical issues and how Sanders is likely to address them:

Transition: As The Nation pointed out in a widely read article this month, no single payer bill yet has really explained how to move from our current system to the new one, or how long it should take to avoid total disruption. The Sanders bill is likely to make the transition gradually, by lowering the Medicare eligibility age over time and providing a government-run "public option" for everyone else.

How to pay for it: This is where the California single-payer effort got bogged down, and the Sanders bill isn't likely to provide much of a road map either. That's because the Sanders team doesn't want to get caught up in fights over the financing. They just want to start the debate over whether health care should be considered a right, and then work out the details later.

Role of private insurance: Even though single payer can be done with private insurance companies (within a government guarantee), the Sanders bill won't have a big role for them, other than providing supplemental insurance. That could earn them some powerful enemies: As liberal health care expert Zeke Emanuel points out, if health insurance companies are cut out of the picture, "they have a existential threat and will oppose with everything they have."

Benefits: There's a lot that Medicare doesn't cover right now, and the benefits are more geared to older customers than working-age adults anyway. Sanders is likely to rework the benefits by basing them on the Affordable Care Act's “essential health benefits," to make them more appropriate for all age groups.

What to watch: Sanders is sure to face tough questions, and so will any Democrats who run on single payer without thinking through the implications . But some Democrats think it's smart politics not to provide too much detail just yet. "The bells and whistles of a single payer system are a political mine field," said Chris Jennings, a former health care adviser to Bill and Hillary Clinton. "They should be avoided and are unnecessary for now."