For the past 3 years I've been fermenting and serving from the same keg, with 97.63% of the beers being NEIPA's that required dry hopping.
When it came time to dry hop, I would get a CO2 line ready and once I pop the keg lid I would begin running CO2 into the keg with a goal of producing an outflow of CO2, hopefully reducing O2 from getting in.
I would then pull out my iSpindel, dump the hops in (commando), secure the lid, build a bit of CO2 pressure, and then do 10 or so CO2 purges.
This process has worked for me with avoiding oxidation. The NEIPA's continued to look like fresh OJ & taste good until they kicked (1-2 months).