Below is a relatively easy way to ensure low oxygen exposure to your beer. It builds on ideas presented here lowoxygenbrewing.com's guide to purging.
Once you've pitched your yeast, and sealed the kegs, hook up the jumper from the gas-in post of the fermentor to the beverage-out post of the receiving keg (so that the CO2 is fed into the bottom). And then hook up a blow-off tube from the gas-in post of the receiving keg to jar of water + alcohol
The keys to success are:
You can still use the technique with a carboy. Use a silicone tube to connect to the airlock or an elbow inserted the stopper. Connect a barbed beverage disconnect and attach it to your purged keg. Now make your blow-off tube for the keg using a barbed gas disconnect and vinyl tubing
If you haven't trimmed your dip-tubes you may need to get past the first cloudy bit of beer/yeast. Attach a cobra tap to the beverage-out post and your CO2 to the gas-in. Capture this first 250-500 ml in a mason jar. Use the liquid on top to test your SG.
Hook up your kegs by using a beer line with two beverage-disconnects on it. Attach these to the beverage-out posts, and your CO2 to the gas-in. Lift your PRV and turn it so that it stays open. Apply some pressure via your regulator and presto!
You can still use pretty much the same technique if your fermentor has a valve on the bottom. Use a silicone tube to connect a barbed beverage disconnect on one end and connector to your fermentor valve on the other end.
If you have a spunding valve you can get the beer to naturally carbonate itself by simply disconnecting the the blow-off tube and monitoring the pressure.
Lowoxygenbrewing.com recommends transferring the fermenting beer with 5 gravity points (or 1 plato) left to a serving keg. This obviously requires that you are confident about your expected FG and that you can either take samples, or have done this a few times and know “when” there are about that many points left.
Having tried both approaches I prefer to simply remove the blow-off tube and do a counter-pressure transfer to the keg after the fermentation is complete. Of course, this is only possible if the primary fermentor can handle pressure.
Having read about counter-pressure transfers in a BYO article I decided I needed to start doing this. Since I'd already purged and pressurized my serving keg with fermentation CO2, I was ready to go [see the section on spunding above].
I used a cobra tap to bleed off a bit of beer and confirm everything was Okay, and then put it away. Next put a spunding valve on the serving keg, hooked up a liquid jumper between the two kegs (bleed a bit to purge that line of O2) and then hooked up the CO2 tank to the fermentor. The beer itself only had about 9PSI of CO2, so I set the tank to just over 10 PSI, and then used the spunding valve to slowly vent CO2 by setting it to about 5 PSI. The beer started moving! I just watched until I noticed a bit of foam at the end. A nice gentle transfer.