Smart Campaign Flow Question

This should be easy for someone to answer. I need a little clarity.

We have a simple smart campaign (email blast)

An audience ran through the campaign already and another audience will be loaded into the static list in February.

The January audience received a single Welcome email.

Now we've been asked to add a second email to the flow, and send it to the January audience and everyone who enters the campaign thereafter.

We believe we need to create a smart campaign that sends the 2nd email to everyone who already got the first email - just non-openers actually.

As February rolls around we'll have a new list of people added to our static list; they'll run through the campaign. Before that, though, the plan is to add a new wait step then a send email step that sends the 2nd email to non-openers of the first email. We want just the February people to run through this. We don't want the January folks to get that Reminder email again.

How would you go about this to ensure no problems?