In homebrewing, you will not eliminate exposure to oxygen. You just minimize that exposure. Do what Boo Boo said, and also minimize splashing while bottling. Chances are, there is some CO2 dissolved in your wort that also protects you a bit. However, the only time I found any comfort in that thought was when I was bottling. I figured whatever evolved out of the beer that went in the bottle also helped purge the bottle a bit.