SqueezeBox,
If the bass line is the main problem you are having with BB, then I would suggest the following. Pick a style as close to the original arrangement as possible. Search the web for the sheet music (song) you are trying to duplicate, that has the correct bass notes for the song. Use the edit function of BB and change the bass part to match what you've found in the sheet music, or you can make a midi file of the bass part and import that into your arrangement. Turn off the Bass in BB, only if you imported midi, and play your song. I use the latter technique when I make CD's for people. The bass line is very important and it needs to be right because it carries the down beat of the whole song. The only problem is that it takes a little more time to produce. PS. If you use the edit function to change the bass line, be sure to save the arrangement or you will lose what you've just spent an hour or so doing the next time you play the song. BB regenerates everytime the song is played so you get a slightly different version each time.
All in all, you will enjoy working with BB. It is a very powerful piece of software, along with it are a bunch of powerful experts here in the fourm, excluding myself, that can and will help you through your learning curve.