Classical Guitar Technique: Essential Exercises, Scales, and Arpeggios " (Bradford Werner)
Practice scales using both Apoyando (rest stroke) for power and Tirando (free stroke) for agility.
Maria was impressed with Emma's progress and encouraged her to continue working through the book. "You're doing great, Emma," she said. "But remember, technique is only a means to an end. The real goal is to make music that touches people's hearts."
References & further study (books to consider)