FWIW, I don't like the shaking method. IME your likely to either over or under due it. I would suggest 36 hours at 30 psi on a cold keg, or 48 hours at 30 psi on a room temp keg while being chilled in the kegerator.
IMO the shaking method isn't any faster as you have to chill...and if you over carb, it's an effort you don't want to experiences.
Also, why would you want to disconnect the gas??? If you have forced carbed by shaking, just leave it at serving pressure, say 10-12 psi?
Also, if there is any beer leftover, you will likely find it far superior after a week or two in the cold box!!!
Have fun...just realize this will yield fast beer, not the best beer by far IMO.
Wilserbrewer
Http://biabbags.webs.com/