Mark, here is what I think, and it may be all wrong But, I figure that if I transfer at about 1.010 +/- a little, I don't have to be too concerned about oxygen because as soon as I transfer I put a air lock on it. The wine is fermenting and producing CO2 which puts a CO2 pad on top of the wine, that will keep the O2 out. Also since its in a carboy with a air lock, it needs the extra O2 to finish fermenting. I don't rack it from the primary to the secondary, I have a paint strainer bag and it fits good over a 5 gallon bucket, I pour the must into the strainer bag a little at a time that is in the bucket. If you'll hold the strainer bag up and let the juice drip out you'll have less krud (Lee 's ) in the secondary, but that's not what I do, I squeeze the day-lights out of it to get all the juice. The krud that you get when you squeeze it will settle out pretty fast, a couple of days at most. As soon as it settles out pretty good, I'll rack it, before it quits fermenting so I'll still have my CO2 pad.
That's just the way I do it. A lot of folks here ferment in the primary to dry, and some just keep it in the same bucket till it's finished. As I have read here a bunch of times, "it's not a science". There are several right ways and several wrong ways and a lot of "My Ways". I believe that most folks here will tell you that what-ever works for you, keeping in mind that there are some right ways and some wrong ways.
Semper Fi