| First, don't worry about whether something is impressive to others, if that is why you choose to learn an instrument or a new playing style then you are doing it for the wrong reasons.
Second, you should practice regular styles (picking, fingerstyle) for a few months before trying advanced techniques
To answer your question, go to victorwooten.com and find the lessons section. Watch the video on Classical Thump, this demonstrates slapping and double thumping (a different form of slapping, you'll know which is which)
Hope that helps, Welcome to the lows
Adam Barkley | 
