One thing that I've tried (to varying levels of success) is to use that time writing unit tests. It's visibly productive, nominally helpful, and incredibly useful in picking apart what's actually going on under the hood. The two biggest challenges I run into are managers (including engineering managers) who insist that unit tests are a waste of time and codebases that retard attempts to break things down to workable units.
One thing that I've tried (to varying levels of success) is to use that time writing unit tests. It's visibly productive, nominally helpful, and incredibly useful in picking apart what's actually going on under the hood. The two biggest challenges I run into are managers (including engineering managers) who insist that unit tests are a waste of time and codebases that retard attempts to break things down to workable units.