I was working on a mix this afternoon, and reached a break-point with drums, piano, bass, 2 x guitars and a banjo all coming -together like one lovely very big and very complex instrument. I had it just about there and was struggling to get the drums to sit properly - eventually achieved with 1.1. dB of low shelving-boost at 330 Hz and 2.2 dB of high shelving cut at 1.5 kHz. using the (at this time) new IK Multimedia EQ81. Just like that - it all came together. I grabbbed a pen and the book, and realised that I actually had no idea what to write. The numbers are just chance - just what happened to work for this particular job. The clever bit (if there ever is one) was to know, or to work-out, or to guess that the kit needed a different frequency envelope - deeper and less bright; but I didn't work any of it out - I grabbed a low shelf, boosted it and slid the frequency centre until it was right, then fine-tuned the boost. Same again for the top-end cut . The actual adjustments took less than a minute and it's one of the most satisfying moves I've ever mixed. And I don't know how to write it in my special book.
The point? Well, it's easy to get caught-up in how clever all the folks writing books and articles in magazines and online are - but the reason that they get good in the first place is because they practice unti they know what they want to hear, and develop some instincts for getting it. When I tell you that I used +1.1 dB of low shelf at 330Hz, don't think "how clever to be to know to do that", I just read the numbers off the dial after it sounded right; the numbers just tell you what you've done, they don't make it happen.