** this is what I do**
immediatley after keggging I hook up gas, and purge all air out then fill it with gas, dissconect and let sit until I want to carbonate, usually immedately. Typically I will let tthe beer sit 3 days with 30 psi. Less psi = more time, this decision is up to the brewer. Then bleed off CO2, turn regulator down to serving pressure ~8psi (depends on your system, lines, temp, etc...) then hook gas up, turn on then pour a pint.
Kegs should be treated like babies, the impatient shake babies