I too am in the new to slapping boat. I thought it was fairly straightforward until today, when I bought a copy of Victor Wooten & Steve Bailey's Bass Extremes book. I always thought of slap as a technique best suited to a 4-string bass. But all of Steve's lines are played on a 6-string fretless (how does one get a slap sound on a fretless - I used to play a fretless), and Vic plays a tenor bass tuned A-D-G-C. Some of the lines are adapted for 4-string.
They suggest tuning a spare 4-STRING A-D-G-C or a spare 5-string E-A-D-G-C a la Steve Swallow (who is not a slapper). I guess I'll just pull out one of my many spare Fodera Victor Wooten Signature basses out of the closet ;-)
Then there's Vic's slap techniques. Suffice it to say that much shedding is involved. Throwing a Zeppelin CD & playing along is starting to look really good right now.
I hope this doesn't scare you off, Mab ;-)