Playing Cooler Chord progressions, doesn't always mean using some kind of bizarre diminished chord. In this case, I'm going to talk about using just a plain of minor iv chord. So you can take a progression in D Major like this, D, A, Bm, and G, which all come from the key of D Major. So it's typical to refer to this chord progression as a I-V-vi-IV (1-5-6-4) progression, because those are the scale degrees from which these chords are built within the key of D Major.
But what we're going to look at is instead of having a major IV, we're going to have a minor iv. So, this is just as simple as going from a G Major chord to a G minor chord. And then putting that back into context with our I-V-vi-IV... you wind up with D, A (or A7 in this key), Bm and then G minor. It's a great way to just kind of change up the way that your chord progression ends. It's a really simple but also interesting way to end your chord phrase.
Check out Part 1 of this series about Reharmonizing with Half-Diminished vii Chords
Also, check out Part 2 of this series about Reharmonizing with Fully Diminished Transition Chords