Fletch got me up to speed on this last year.
At first, the "extra workouts" should be geared for recovery. Whatever you can do to set up for a better real workout. Anything that hurts, or takes a little extra work to get loose and warmed up in the gym, hit it at home.
Easy goodmornings with a band to get the blood flowing the day after squatting. Or if you're more messed up, you can do all that rehab junk. Peterson Step Ups for the trick knee, or clam shells for shitty glutes.
Then you can do all that stuff you "should be doing." Band pull-aparts, fire-hydrants and dead bugs. 100 extra band pushdowns and a couple jumps. Whatever "You Should Be Able To Do This Challenge" tip you read recently.
Start easy. Make sure whatever you do doesn't impact "real" workouts. Then just keep adding a little at a time. Gradually pick more challenging exercises, and drop the easiest stuff.