I see no harm is starting Natural Brilliance while doing Abundance For Life they are closely tied.
You can begin by listening to the last CD daily for a week before starting the course if you want.
You can do Session A one morning and session B the next so you can still devote some time to the Abundance For Life CDs. When you do start the course you will want to listen to Paul's coaching and the Paraliminal that goes with that coaching at some point during the day. So I wouldn't bother doing it until there is a slow period for you with the Abundance For Life course. You do want to focus 100% on each course. If you're strapped for time the last thing that's going to give you focus is doing more in the time you have available.
Alex