Is 20 minutes a day enough to master noun cases for the YKI test?

I’m a busy professional trying to prepare for the YKI-tutkinto, but I only have 20 minutes total during my commute to study. I’m finding the case system (specifically the inner vs. outer locative cases) really overwhelming to review in such short bursts. Should I prioritize heavy memorization of tables, or would using Chickytutor.com to simulate short, intensive dialogue practice be a better use of my limited time for exam prep? I am asking specifically about learning Finnish, not a generic study routine.