You picked a very bad time to learn AE. A Horrible Time: you're trying to to fix a lot of video on a deadline. That's just about the worst.
Okay, let's start with a basic question: how good does this have to look? Like it was shot with the background out of focus, or will you accept areas around the people that are still in-focus?
It will probably be faster for you to get the Premiere issue fixed, and do it the way you already know.
Furthermore, you will have learned why people say over and over again, "Never upgrade your software in the middle of a project."
I'll give it a try. Thanks...
This tutorial will show you how to use Mask Tracking and Effect Masking in AE:
Stu uses Colorista but you could use a blur instead if you have AE CC 14 or even PPro CC 14, but I'm kind of thinking you should on concentrate on finishing the project before diving into what can potentially be a very difficult masking and roto project for a beginner. Depending on the shot I budget on average about 2 hours per minute for Roto work. It can take a lot longer. If the preproduction planning resulted in a shot that is easy to roto then it can go a lot faster than that. If you are going to try Rotobrush then you MUST watch at least the basic tutorial for the tool in this list: Roto Brush | Adobe TV. Roto Brush is not intuitive and you will need to take some training to use it.
Mask Tracking is essentialy a loose fit automated rotoscoping technique. Rotobrush can, not necessarily will give you much tighter masks. The 'will' part depends entirely on the shot. As far as telling the story, how important is it to simulate a shallow depth of field? How important is it to have the mask fit the subject perfectly?
A screenshot of your interview would really help us come up with some suggestions for a solution that is not based entirely on assumptions made with no real knowledge of the problem we are asked to solve.
I was feeling pretty lucky that the new PR 2014 had the mask and tracking. I got into this mess when I tried to rent a second 5d Mark III from Lumoid for my two camera shoot. They missed the first day to ship, said they were going to ship it overnight the next day and never called FedEx to pick it up. I ended up having to use my XF305 that didn't match color or DOF. It's been a nightmare ever since and I won't make that mistake again.
Thanks for all your suggestions and I'll wait to try the Roto Brush until the 45 minutes of footage has been edited down to the final 2-3 minutes.