[Question] How do you refine your technique?

Dear r/piano,

I'm a multi-instrumentalist who started piano first at 8 years old. I had the pleasure of playing at All Ohio Piano Ensemble, and for various composers. At 18, I taught for a year at a local shop in town while taking the role of assistant musical director / conductor / pianist for my college's production of Little Shop of Horrors.

I'm hoping to get back into the swing of practice this summer and do some serious work refining my technique (my theory chops are pretty sharp, could go over extended harmony / its inversions / scales other than major & minor types and pentatonic and their functions a bit more). I have the Hanon Virtuoso Pianist book and an Alfred Group Piano book that I intend to use for exercises and developing scales / arpeggios.

Can any of you suggest other practice materials that might be beneficial? Any books in particular for voice-leading through progressions containing examples / stock voicings to use? I'm not sure whether or not to include a difficult piece on the side like, say, Fantasie Impromptu, that would take months and would be learned in a manner completely dedicated to increasing my ability to play the tune (one hand at a time, metronome practice andante -> a tempo, phrase-specific repetition for practice, addressing specific pencil markings on the score, etc).

Also, are there any pianists making a good living teaching without a music degree? I will finish my degree in Music Production / Music Minor this December and am fairly certain it is a one way ticket to flipping hamburgers at McDonalds... I'm hoping to start self marketing and teaching multiple instruments out of my parents' home, but will be competing with my former employer / multi-level music studio I taught at in town as a 1099 employee. Would love advice / success stories. Thanks!