well currently I half fill my kegs with 60 degree sodium percarbonate solution and give them a good shake, let soak for 10 mins and use the increased pressure to push SP solution through the dip tube and liquid post and leave to soak for a good 20 mins, then turn upside down and soak for another 20 mins or so to give the gas post a good soaking. then when I rinse out will flush through with water then fill with starsan and flush starsan through posts and leave until needed.
I can't be bothered to disassemble every time. I don't think it's necessary. there is not much to the posts - its a simple spring and poppet valve so flushing through means the cleaning solution contacts all the surfaces and a good active cleaning solution like Sodium Percarbonate or similar with to their thing.