Filtering finished beer

I am in the process of putting together a filtration system using a simple 5 micron cartridge filter and a 0.5 micron cartridge filter in 2 separate filter housings.  The keg of unfiltered beer will be connected to the filtration system and the discharge of the filter will be connected to a clean and sanitized corny keg.  I will use CO2 to push the beer from the first keg through the filter and into the clean and sanitized keg.  My questions are these:

Do I have to fill the sanitized keg with CO2 before I begin to filter the beer to prevent oxidation?

Will I use a lot of CO2 to push the beer?  I currently have a 5 lb CO2 cylinder and can get about 5 or 6 kegs out if it.

Oxidation is a big cause of flavor instability and off flavors.  I always rack on a blanket of CO2. So yes, purge the keg with CO2. I send it down the dip tube pushing the air out the top. Takes only couple psi to run thru a 5 micron filter - your gas use will be minimal.

So once you run the co2 into the keg, you vent, then take the top off and stick your racking tube down at the bottom or do you transfer some other way?  Thanks.

If you attach a beer out qd to the end of the racking tube you can push the beer down the beer out dip tube.

Ahhhhh, that makes sense.  I’m going to start doing that.

Yes, correct as above.
Also, make all beer transfers under CO2.
I use 7.5 gallon glass “acid carboy” fermentors with “acid carboy caps”, you know the maroon colored ones with two spouts sticking straight up. Purge all lines/racking cane with CO2.  Stick the racking tube in the center spout with plastic tubing connected to the keg “out” port. Stick the CO2 into the second spout of the carboy cap. About 4-5 psi CO2 and the beer will flow out the fermentor into the keg, which already has a CO2 layer as described above.  This is a solid beer transfer under CO2.