Ok, so I'm 15 and I just turned my 4-string into a fretless.
I just started watching Blue's Clues again because there's an inside
joke I have with a really close friend about Blue's Clues.
I was watching the show and I heard this bass line and I was like
"Dude that's an awesome bass line!"
To get the timing, sit through the show for about 10ish minutes,
which is usually about the time Steve finds the first clue.
When he drawing the clue, this is the bass line.
By the way, it's done on a stand-up bass, which is fretless, though
it can be done on a freted.

G|-----------------------------------------------------------------|
D|-----------------------------------------------------------------|
A|--50-3-2-2/9-7\2-0-4-5--3-2-2/9-7\2-0----------------------4-5~~~|
E|--------------------------------------3-2-22/8-7-10-12\7-5-------|

OR, If you're not that good going up and down the neck, you can do this:

G|---------------------------------------------------------|
D|--------/4-2\------------/4-2\---------------2\----------|
A|--50-3-2-----2-0-4-5--3-2-----2-0------3-2-5---2-0-4-5~~~|
E|----------------------------------3-2-2------------------|

However, the first one's better because the cool slides that get thrown
in actually work.  If you don't know when Blue's Clues is on, it's on at
10am on Nickelodeon.  If you don't wake up that early, or aren't home at
that time, it's a very bluesy sounding walking bass line, and look it up 
on Youtube.  It'll be on there somewhere.

Steve Rocks!  Joe Sucks!