This is what I want to do and is shown in the pic.
Fair enough. The reason the guy in the link is pressurizing the kegs is because he is filling them with beer that is already carbonated. Without back pressure on the receiving keg, CO2 would start coming out of solution and it'd be a foamy mess.
Pressurizing them alone won't get rid of all the oxygen though; you're still going to want to do a proper CO2 purge.
How do you know when to stop filling the keg before beer shoots out the gas tube?
If you chill the beer before you rack it, you will see the line of condensation creeping up the side of the keg as you fill, and it'll give you a good idea of when it's full.