When you open a BB SGU in Realband it should load everything, there was a bug if you had RealCharts enabled (right click on a track > Enable RealCharts) it would not generate the drums but not sure if that was fixed, but you can just generate them up manually in realband, also make sure you have the RealTracks/Drums folders set in Options > Prefs > Song Generation > Paths.
In Realband you can generate up as many tracks as you like, generate MltiRiffs anywhere, easily edit sections and you can actually see the wav files.