I was going to recommend reading out loud as a way to practice speaking with proper grammar, but it sounds like you already do that. I've found it helps to make sure I'm "thinking out loud" when I talk, rather than focusing on saying words. It's hard to describe but definitely feels differently. I find if I focus too much on saying words (without stuttering) I lose the brain's natural ability to form coherent sentences. Incidentally, reading out loud was a huge breakthrough for me as well when I was in my 20s (I'm 40 now). I wouldn't say I'm "cured" as I still have to manage my stutter and it still comes out in some scenarios, but it doesn't really get in the way of communication any more.