Here's a simple little Tommy Johnson-style 12-bar progression in D (with 2-bar intro), based on what Tommy uses in "Canned Heat Blues". The groove that is played in bars 1-2, 4, 9-10 and 13-14, where you insert your pinky on the 4th fret of the 3rd string to alternate between a regular D chord and a D6, can be heard fairly often in old blues recordings. I don't know whether that's a testament to Tommy's influence or whether it was commonly played even before Tommy, but in any case it's easy to play and it sounds kinda nice. Not real bluesy, though, unless you manage to combine it with Tommy's ghostly, moaning singing style!
Note that the fingerings in the beginning of bar 3 (the first bar of our 12-bar progression) and bar 5 are simply variations of a D chord. Bar 3 features a nice slide down the neck from this 2-note D fingering:
To this 2-note D fingering:
Bar 5 simply drops from a D to a D7. In bars 7-8, you're basically playing out of this G7 chord fingering, occasionally lifting your index finger from the first fret of the first string and then putting it there again:
In bar 11, we go from an A chord to an A7, much the same as we did with our D chord in bar 5. Simple stuff! Now if only I could sing like Tommy...
By the way, when I play blues in D I prefer to drop my 6th string to D and play in drop D -- then you can twang on your 6th string for extra effect whenever you're playing the I of your I-IV-V progression.
Here's a brief sound sample of what Tommy sounds like
(note that it starts in the equivalent of bar 5 of my tab, and after playing bar 14 he goes back to bar 3). He does play this verse a bit different from my tab when he's playing the G7, but he's still playing out of a G7 fingering. Plus, this gives you an idea of how good old Tommy used to sing!