Look at some Meshell N'deggiocello. She plays a whole lot of relatively easy bass lines, but she throws in some super creative stops and lines. The classic is "If That's Your Boyfriend"
http://www.youtube.com/watch?v=8so3qdNlICE (Bass great Yossi Fine actually takes over after the intro on this clip.)
Don't worry about the technique during the slapping part, get the notes. All of them, and be wary of the timing. The little clicks on the upbeats. Getting all the notes and the timing is WAY more important in being funky then slapping. Many, many funky bass lines aren't slapped.
Finally, don't over play. If you watch any of the great funk players, they really don't hit the strings very hard, and they leave alot of space between the notes. Funk does not mean a crazy, agressive bass line, it's actually the opposite.
Here's a good tutorial from Ms. N'deggiocello:
http://www.youtube.com/watch?v=srCZE...eature=related
I like her line at 1:16 about "stripping away things" making the music groove harder.