SHhh-pat is a gradual process that will result in putting them into their cot wide awake, them rolling over and going to sleep.
You have to start by not feeding or rocking to sleep any more. With the fed to sleep babies you should move it earlier on in the bedtime routine so bath if you do that (we didn't every night due to dry skin), pjs, milk, sleeping bag (if used), quick book and then start to settle.
To begin with we just held him, patted his bum and made the shhing sound. It is meant to replicate how a heartbeat sounds inside of you. Just persevere with this and they should go to sleep eventually. Make sure you start the bedtime routine early enough so that they are not overtired when you try and soothe them to sleep.
When this becomes easy, you progress to putting them down in their cot and shh patting them there. The time it takes to shh-pat them in their cot should reduce and reduce until they're so used to the routine of it that they eventually just go to sleep. It should take about 2 weeks.
With regards to feeding at night, its best to set a time limit of say 5 hours from bedtime. Its realistic for a baby at 4 months to still want to feed twice at night. If they wake before 5 hours, or however long you think they should be going between night feeds then settle them via shh-pat instead.
If you choose to feed to sleep and it becomes a negative sleep association then your baby will want to be fed back to sleep everytime they wake up. This will pass on its own but I always felt better doing something to tackle it rather than just accepting it (I NEED sleep!)
I hope this helps if it is something you're interested in.