How many nights of sleep training before it works?

So we are planning to sleep train our 7 month old in a few days. Starting with bedtime, putting down awake and walking out. Shoosh/pat when we go in to check-in. No pick ups.

Mentally preparing for a long few nights and being emotionally and physically drained by it all.

Curious to know how many nights it took before the crying at bedtime stops and baby learned to put themselves to sleep? And how long before the multiple wake ups overnight stopped or reduced?

Our little one cant connect sleep cycles, so it's constant wake ups overnight. Very exhausting! And he also seems to be fighting the third nap so might be ready to drop to 2. Lots going on!