EGT will always be more accurate then the fuel flow gauge
Yes, but with a few factors: If you're using a scanner type EGT (not common in rental aircraft), you can see which cylinder is most lean. It is very possible that the most lean cylinder changes from one to another based upon power setting. Lean to the most lean cylinder - obviously! In my O-200, the most lean cylinder will vary from one to another by more than 100F, depending upon power setting. 2450 RPM gets me the closest to all cylinders having the same EGT temperature value.
If you're using a relative EGT (the old pointer type, with no numbers), finding the peak is pretty easy. These are pretty safe, as once you find peak lean, you richen it up as required, and you certainly will not be more lean than you intend
for that cylinder, though you might be more rich.
If, however, the EGT is the type with tells you a temperature as a number, that value can have errors as a result of the position of the probe in the exhaust stack. EGT probe manufacturers often describe very specific positions for the probe tip, both relative to the diameter of the pipe (usually in the middle), and distance from the exhaust flange (4" - 6" seems familiar). Sometimes the exhaust system geometry prevents installing the probe in the right position, and sometimes it's just installer carelessness.
In any case, get to know how to interpret the information your EGT gives you, and remember that unlike many other instruments in the plane, it is very unlikely that the EGT has been calibrated, and confirmed to be reading correctly
as installed.