Source: It's exactly what I do (0.6 FTE job + part-time MSc).
From personal experience, I would say it's harder to find something part-time up front. Telling your current employer that you want to reduce your hours, for the reasons you describe, is what worked for me. You need to be in a position where they are happy with your work, and you need to clear any doubts about this change having any negative effect on your team.
From my perspective, being part-time greatly discourages me from micro-managing: I just don't have the free time that might lead me down that negative path.
Finally, my employer gets way more than 0.6 FTE of work from me (and I don't do extra hours). IMO they get more "bang for their buck": I concentrate on what's important, and work through things more efficiently.