Yeah, good tip regarding 12 bar blues.
When I started out I remember being shown this and just realizing I inherently knew it already flow-wise, as it's such a frequent backbone of many songs. It will help you anticipate changes and see the chords as part of the whole progression. And once you know it, you'll recognize it when you hear it in many musical genres.

As far as the strumming, I suggest trying out the intro (and general progression) to "Pride & Joy" by SRV. You don't have to hit every masterful nuance of his of course...just "wing" it where you can, but just to get the idea of that walking bass with rhythmic upstrokes.