I find that the combination of the aforementioned high action and the 'Hook" technique can really make you sound like a double bass player. Depending on your instrument, pluck roughly where the fretboard meets the bass with the full length of your first two knuckles on your first finger. Double bass players often use the same technique in a vertical position. If I get some time tonight, I'll make a quick video demonstrating what I mean.
Compression can help. I use my Markbass Compressore with the gain around 8 and the ratio around 4 to add some tubey goodness.
Mark Hoppus Signature Bass Club Member #13