Once you are comfortable playing triplets over a constant bass, try adding some extra bass notes on the third part of the triplet as shown in the following examples. This may take some time to develop, so practice example 299 until you are comfortable with it before tackling example 300.
This one is a slow Blues in + time using the same technique. The left hand part may be difficult at first, so take it slowly and be sure to count and tap your foot.
Now try this 12 Bar Blues which uses chords over the shuffle bass and also contains bass runs between some of the licks and chord changes.