Until I switched to the conical, I always dry hopped in the secondary. I keg, so it's easy to hit the carboy with CO2 prior to racking the beer over, so I didn't worry about O2 touching the beer. I put the hops in, hit it with CO2, and racked over. IMHO, I think this resulted in a better beer. I got the beer off any trub, dead yeast etc. There was enough yeast left in suspension to clean up the flavor, and it resulted in a clearer beer. After dry hopping, I'd cold crash it for 3 days prior to using gelatin in it. Super clear beer!