Hi Pete
Welcome to the forum
I always like to direct new users in your situation to:

http://www.pgmusic.com/videos.user.htm

and then to watch the video set there titled:

Song From Start to Finish - BIAB, RealBand, & Reaper
Author: Dan (aka Shockwave199)

It's a good example of using BIAB to rough out a song, then Real Band to add Realtracks to "flesh it out" and then transfer it to Reaper (or in your case Cubase) for final tweaking.

Have fun learning both BIAB and Realband and realize that the people in this forum are a wealth of knowledge and eager to help newbies with any questions or problems you may encounter.

Have a good one,
Carkins