I recently came back from a 12+ year break. I wasn't a high-time pilot to begin with, and I think the instructor signed me off with a BFR of 5.7 hours, and 2 hours of ground. He would have signed me off with less, but I asked for a bit more. For one, I started flying in a different region than the one where I trained originally, and the issues we have out here are different than the ones I originally trained with (mountainous terrain, high density altitudes, regular strong cross winds, etc). And, like most people who have come back from a long break, I've taken a couple of other rides with instructors just to brush up on things.
As for the studying, I did some reading through the same texts I used when I worked on my PP and Instrument years ago. I replaced my FAR/AIM with a new one, and I spent time online watching Youtube videos just to refresh my memory of other little things I may have forgotten.
The instructor I worked with was someone who had also come back to flying after a long break, and he was able to relate to the things you need to relearn when you come back. The first hour felt like a soup sandwich in some ways, but it quickly improved again after that (just as the instructor suggested it would).
EDITED TO ADD:
Don't be in a big hurry, either. It sure isn't a contest to see how few hours you can log before feeling proficient again. I've logged 8+ hours of dual time since I came back, simply because I want to make sure my skills are sharp and acceptable before I put my family at risk. Someone recently asked me why I was bothering to pay for an instructor when I was current and legal to fly on my own… the simple answer is that I've got a lot more riding on a successful flight these days than I did back when I was first learning to fly. It is a perishable skill, and I don't want to end up with my story on an NTSB report someday.