"Plucking each string without looking"...I am self taught on the guitar and learned from a book on classical guitar ( Wish I could remember which one now. ) I am 66 now...I had the same problem when I started. What I found useful, for me, was to play a line or small portion of a piece over and over until I could play it by rote. then I would move to the next line of the piece, repeat the first without looking and add the next till I could play them both by rote...I would repeat this process until i could play the entire piece by rote...Worked for me...I hope this helps.