Very good. Does it matter if you purge before or after racking? Also I saw an interesting video where a guy put his dry hop in the secondary before racking. thought it was a cool idea.
You have to purge before you rack - CO2 is heavier than O2, so the CO2 will tend to sit in the bottom of your next vessel. So, you are racking into a mostly CO2-rich environment. You want this. I place my dry hops into a purged keg, into the canister I use, and then rack on top.