I would definitely prefer to do a slow gentle approach rather than a quick one, especially as I have awhile.
In that case the things you mentioned in the OP (PUPD and CIO) really aren't necessary at 6 months old. These methods that make babies cry would only be necessary in a mum who wants/needs baby to sleep more independantly RIGHT NOW. They are the urgent "something must be done" sleep training methods if you cannot continue how things are any longer.
For you charlie13032017, prefering the slow gentle route, there's no reason to put yourself and baby through the stress.
Having said that, there are things you can do to slowly progress towards independant sleep. The Pantley Pull off from the No Cry Sleep Solution is worth looking into. It's reasonable to expect to have stopped feeding to sleep by 18 months if you are consistant with that.
The concepts behind NCSS begin with realistic expectations. These are not things that will have baby sleeping independantly any time soon, these are not quick fixes. But more about making small steps (that cause no crying) towards independant sleep.
The Pantley Pull-Off is the first step in this. It means unlatching baby when nearly asleep and rocking to sleep instead. Then progressively unlatch soonrsooner until feeding to sleep becomes rocking to sleep.
Then follow the same process to move from rocking to sleep to lying down reassurance. So stop rocking earlier as time goes by. Then baby gets used to sleeping stationary in your arms, then from stationary cuddles to gradually putting down and reassuring in the cot. Use of a comforter object comes into play nearer 12 months too.
So for now, all you would need to do is see if you can unlatch baby once dozing and get to deep sleep without nipple in mouth. This is not meant to be stressful or create any crying. Then do this increasingly earlier in the feed.