I'm sure you are aware of GM norms.
Aside from that, it's my understanding that you must devote a certain amount of time every day to studying the various aspects of the game (Opening theory, middle game, endgame, strategy, tactics and all things in between). A big part of it is studying your own games deeply with computer analysis and understanding the reasons for the moves the computer suggests and why some of the moves you made weren't as good.
It also helps to have a powerful memory. Most GM's have highly trained memories. They can recall dozens (or hundreds) of games they have played and studied.
You're already an FM so I'm sure your aware of most of this stuff. I'd say just devote a few hours every day to studying chess and especially studying your games with computer analysis. It will pay off....maybe not to the point of achieving GM, but stronger than you are now.
I am wondering how would you attempt to reach GM level? I have about 2 years of free time, and would like to devote some time to chess.
I reached 2300.
an interesting epiphany I got was if I were 2200, or 2300 in chess, then all I would need is to acquire rating in the following fashion:
openings - 100 ratings pts.
middlegames - 100 rating pts.
endgames - 100 rating pts.
I have become fond of mnemonics in chess, more so to create a formal mental track of knowledge and also to supplement the learning.