On the right track. A few comments. Neither of you mentioned the origin of your kegs so I'll assume used.
Sometimes used kegs haven't really been thoroughly cleaned before sale. Take them apart and soak everything if it appears there is any soda syrup residue or smell. Make sure to separate the poppets from the posts for cleaning. Be sure to put posts and dip-tubes back in their original location.
All 5 O-rings should be replaced on used kegs unless you know it has already been done. Use a food grade lube product on the 0-rings like keglube.
Sometimes it takes more than 10-15psi to seat the lid on cornys. I use about 30psi to seat my lids and check for leaks, then dial back regulator to carbing pressure.
Be sure to securely attach the disconnects to the correct posts.
When filling the keg with beer, use tubing that reaches the bottom and don't splash.
Apply CO2 pressure to seat the lid and then pull the pressure release a few times to dilute the air/oxygen in the headspace. If you don't have pressure relief valves, alternately remove the disconnect and depress the gas in poppet and re-pressurize a few times.