I only put in about 15 minutes of guitar practice tonight. I just did what the instructor from my Udemy curse calls chord pushups. You play the chord, take your fingers of the guitar, flex them out, then put them back on the guitar and play the chord again.
The idea, I think, is to develop the muscle memory so you can move between chords faster. It’s probably not bad for building strength in your fingers either.
I’m getting callouses on three of my fingers, which is helping.