there is a bit of irony here. When you first learn guitar, it is your brain that leads the way. However as you develop skill it is a direct result of developing muscle memory. Muscle memory is where the mechanics of music take place.

I had an experience where I didn't play for decades due to physical problems with my arms. I finally got insurance and got several years of PT. Slowly my arms healed and I started playing guitar again.

I tend to play original music and don't really know a lot of music that I didn't write. The amazing thing was that all the screwy weird jazz chords that I had incorprated into my music were a complete mystery to me when I started playing again. I had written down the names of those chords but could not picture them clearly. But if I just kept repeating the small parts my brain could remember my fingers would jump to those jazz chords on their own. That had nothing to do with my brain and everything to do with muscle memory. As a result I have way more faith in muscle memory than in mental memory.

So though you spend tedious hours working to develop muscle memory, in the long run that memory is vastly superior to your brain. It is also the key to not flubbing parts of the music you are playing. Once your muscle memory kicks in things get easier. Keep at it and don't physical frustration stop you. The process may be tedious. but your are building deep skill that will serve your now and for years to come.