I was taught to lean until the RPM rises slightly (<50RPM) then when it starts to fall again enrich the mixture slightly.
Yes, that sets peak-EGT pretty well.
The efficiency is a flat curve around peak EGT so one doesn't have to be accurate. I've done accurate tests and going LOP
at the same IAS i.e. thrust makes no additional MPG improvement. Any such improvement comes from the acceptance of a lower IAS
And any lower IAS will yield better MPG - all the way back to somewhere near Vbg.