Here is another exercise, which like that last one, can be played on every string. It includes only major and dominant chords. Once you can play it, try it using hammer-ons and pull-offs, and play it in triplets, or in a triplet feel.

Upright players like to use open strings as reference notes, to improve intonation. If you play fretless, this is a good idea, for the same reason. But even if you play fretted, adding open strings to your walking lines adds authenticity -- and extends the range of your leaps on the bass.