E Chromatic Scale in Octaves – Practice in both solid form and broken. Use any logical right hand fingering such as p-i the entire time or alternating p-i-p-m. There are an endless number of exercises for finger independence and stretching but playing scales in various intervals provides an excellent workout and adds musical context and variety. YouTube Lesson Link.
This exercise is from page 104 in my book Classical Guitar Technique: Essential Exercises, Scales, and Arpeggios. The 122 page book includes: Practice Routines, Tips, 100 Open String Exercises, 120 Giuliani Arpeggios, Scales, Slur Exercises, Shifts, Finger Independence, Barre, Tremolo, Common Harmonics, and much more.