You're talking to an audio engineer. 
But sure... there are different schools to this. Personally I think guitarists are picky with their tone so if I do something drastic I'm trying to make their music sound like my music which is not the professional way of mixing. You don't have to put a finger print on everything. And the thing with "perfect" is that there is no such thing. The beauty is in the "flaws" IMO. Like f.ex. every successful actor has a nose that looks like it's been broken a dozen times. That's what makes them stand out. :lol But talking about that would take us off topic.
There is no "correct" EQing technique but if you want to know how it's being taught then 3dB is good general maximum rule for both EQ and compression. Remember that 3dB is double volume. DOUBLE! When you boost over that I would say that there is a bigger problem somewhere else. Low cut and high cut are always okay.
But sure... there are different schools to this. Personally I think guitarists are picky with their tone so if I do something drastic I'm trying to make their music sound like my music which is not the professional way of mixing. You don't have to put a finger print on everything. And the thing with "perfect" is that there is no such thing. The beauty is in the "flaws" IMO. Like f.ex. every successful actor has a nose that looks like it's been broken a dozen times. That's what makes them stand out. :lol But talking about that would take us off topic.There is no "correct" EQing technique but if you want to know how it's being taught then 3dB is good general maximum rule for both EQ and compression. Remember that 3dB is double volume. DOUBLE! When you boost over that I would say that there is a bigger problem somewhere else.
Low cut and high cut are always okay.