It is a boring answer but in my experience nothing beats practice. Distance control drills and I do the cross drill from 3-6 foot where I put tees into a cross to form a cross around the hole and then take 1 ball and start with the 3 footers. Can't move to the next distance until I get all four in. Frustrating yes, boring yes but if you do miss one and start again at least you are getting used to seeing a lot of the nervy distance putts going in. Of course everyone including pros miss so the option is to simply make one putt from each station and then move on and not begin again if you miss. Doing it in a cross fashion will give you varying breaks and idealy up and down hill as wellIt’s the worst part of my game by far I’m hitting it well enough to be in single figures but my putting is really poor if I tracked stats I’d imagine I’d be 15 handicap level
I very rarely threaten the hole from any length above 10 feet and my tendency is to leave them short if they do look like going in
And I’m wobbly with them 3-5 footers
It’s a grim existence on the greens sometimes
I also have one of these and will hit lots of 3 footers witht he outer ring in. Doesn't work as well the further out you go. If I am really struggling I put the smaller ring in. That is very tricky and so don't get frustrated https://www.amazon.co.uk/JL-Golf-reducer-practice-training/dp/B00MRZ7TAA
Once you take the outer ring out and start putting to the normal size hole it looks and feels so much bigger and is great for confidence