Cry it out method tips

We're considering trying this to help with our 4mo's sleeping at night. He goes 4 hours great but then every 2. He also won't fall asleep without being held and bounced and then have to very carefully put him down so as to not wake him. Wanting to try something to help him with good sleep habits and learn to put himself back to sleep when he wakes at night. Please don't just write the names of different methods, please tell me how it works and how it worked for you, how many nights were invested before seeing a difference.