I did find a carbonation tool on Beer Smith (not sure if everyone an see this URL.....
BeerSmith 3 Online) that addressed Carbonating in a Keg. So if I put the Volume of C02 at 2.4 with temperature at 68 f and 5 gallons it shows to carbonate in a keg the pressure should be 28.4 Psi and if I naturally carbonate it shows I should use 2.13 oz of corn sugar. But if I am bottle carbonating it shows I should us 4.26 oz of corn sugar. Looks like if natural carbonating in a keg it is about half the sugar. I normally fill my keg with C02 before racking beer into a keg from the fermenter. So the process would be to set up my fermenter with a sanitized siphon, of course everything (like we all know) will be sanitized after the boil. The keg (sanitized) will have the priming sugar inside and have C02 in it. when the fermenter is ready to siphon, I will open the keg and start racking beer into the keg. Not really afraid of oxygen as this is how I do it all the time with good results. I will leave the keg at room temperature for 2 weeks or more if it needs more time to carbonate, then put it in the kegerator with a little C02 pulling the pressure release valve a few times to get as much air out as I can. I can either serve out of the keg or bottle. In that I am doing a 11% Belgian Dark Strong I plan to bottle as soon as the carbonation is right and leave it for a year. But as we all know I would need to inspect (drink) a few bottles before the year is up.