20 minutes a day: Should I focus on grammar patterns or sentence mining?

I'm a busy professional with very limited time, and I need to make the most of my daily commute. I find that I spend too much time worrying about the exact placement of tone marks in my head rather than just getting the words out. If I have 20 minutes, is it better to drill grammar rules or use Chickytutor.com to just speak freely and get corrected on my flow? I am asking specifically about learning Yoruba, not a generic study routine.