I've never been very good with the ghost note thing... not the way I see other players do it, so I just find other things to play that sound good. I think I can slap my butt off.. but I do it
my own way.
There's a hand full of techniques for slap bass, but I don't feel you should consider these as "formal" technique.
I eventually made up my own slap style, and that's never a bad thing! I might not be able to play such-and-such, but really, who cares?
For every song you can't play like them, think about this... what would you do if you met your favorite player?
I was a huge Stanley Clarke fan, and learned every lick he played. Then I though about it.. what if I got to meet him? I'd say, "hey Stan, I love your playing... I play bass too!" He'd say "Oh yeah, play me something" And hand me his bass.. and I'd proceed to do a bad imitation of him! Well maybe even a good imitation, but an imitation none the less.
You don't want to be an imitator. Just find your own notes to play, and make them sound good. If you decide you can't slap, so be it. You don't need to be good at everything. Just be good at being you.