It helps to have a song with a groove. I was watching TV last night while doodling on a classical guitar. when a commercial came on that used War's "Lowrider" song as background:
YouTube - War - Low Rider
I made up some chords on the spot that approximated the horns' riff. Cool. And it was simple, too. Four chords, easy to play. It doesn't have to be hard to sound good.
That song also have a bumpin' syncopated bass line. Too bad it it's fairly static. Hmmm... when a song has little sustained interest, bung it into a medley. (Rubs chin) the War medley, hmmm...
But yeah, I know what the challenge is. CM is like juggling: you have melody, harmony, bass line, single note fills, rhythmic groove, and you're trying to keep them all up in the air.