What I did was hold out (sustain) the chords to give it that smooth feeling. Every now and then I did some of the melody, but I didn't want people to really notice I was playing an R&B song, just groove with the music. Here are the chords I used:
4/4 time count in [ ]
tempo: 75bpm
[1, 2, 3, 4] Cb / Cb-Eb-Gb-Bb
[1, 2, 3, 4] Eb / C-D-F-G-Bb
[1, 2, 3, 4] Db / Db-Eb-Gb-Bb
[1, 2, 3] Bb / Cb-Eb-Gb-Bb
[an, 4] Ab / Bb-C-Eb-Ab
(repeat)
You hit the bass note once, but hold the chord down.