Jim, it seems the Kombi would be a great place to start since it has a large sweet spot and is generally easy to line up your putts with.  The rest takes practice! Good Luck!!  By the way the last couple of times I saw Scotty at the golf course...Scotty himself has uses a Kombi (S Model) ...albeit he changes around from time to time.

Good Luck! 

Lessons hahahahahah  sorry that's why my old coach used to tell me. I'm not sure if he wanted my money or really wanted to give me lessons hahahaha. but i digress. honestly any scotty is a good scotty. i recommend trying out all of them. find that one that just feels great in your hands you like how the ball feels when it comes off the face and gives you confidence. then Stick with that putter. you can only get better at putting if you use the same putter for a good period of time if your always changing then you never going to have that go to putter. 

Or you could pick up a Bob Rotella book, They are great too. Focus on your fundamentals and as always a constant grip pressure through the entire stroke works wonders