The only problem with using supplements is that there are no supplements for real life. What happens when you have real clients with really tough issues? I suppose if you work for a larger firm, you can always ask for assistance from another attorney. However, what if you are working for a small firm or are a solo practitioner dealing with a question of first impression or some issue where your client's situation puts his best outcome in derogation of common law? To win those cases, you really have to learn how to argue. Supplements, if over relied upon, short circuit the process of becoming a skilled attorney. Don't get me wrong, I use supplements during deadweek to fill in holes in my outline. I didn't find them too useful this time around, though, because the profs test on what they have taught rather than what the supplement teaches.
As to outlining as you go, I think it's possible if you use One Note because you can quickly and easily transfer class notes and case briefs into an outline. While the final outline is not complete until the very end of the semester, you work on it piecemeal during the semester so the final outline is just a matter of moving things around.