Well, since you're still learning, you might want to search these forums for Victor Wooten's technique.
www.victorwooten.com as well as it has some lessons.
Basically, if you want 2 notes on each thumb hit, that's probably the only real solution with good tone. If you want a note and a mute, or mute then note, then you'd want to involve hand slaps. If you can, try learning Vic's method.
-Eric.