The Softest putter I've ever held was a SuperSoft Wizard. I don't know how old it was, but it felt almost like wax, because of how bendable it was. However, the rim still had some rigidity to it. I found it sitting in the sun, no telling how long it was sitting there.
It was pink....not that that really helps you out, just giving as much information as I know about it.
I found the owner and gave it back, so it's not in my possession any more.
I hope that helps a little.
Practice, practice, practice. Especially with players that are better than you. It's one of the only ways to learn new things.