I think we all know this. Whether from personal experience (someone told to do this) or we just read at some online forums, or, we told this to someone.
No matter which version is true from the above ones, the real meaning is still a useful advice. With a probably overly positive attitude I would say it means: Read The Fantastic Manual (as it is definitely answers your question).
I’m in the process of preparing to the summer festivals, where I’ll be the executive FOH engineer (at the 3 biggest festivals in Hungary). This means I have to have a very deep knowledge just about any console that might show up. So basically I have to be able to operate any:
regardless of the version and/or configuration. At first, of course, this is somewhat daunting, but it is a great opportunity to learn the different concepts and approaches that the various manufacturers have. Neither is right or wrong, but they are very different at certain things. Why must I know it all?
Well, because in general, every guy/girl who come with a production has some knowledge about these consoles. Some of them are real experts of a certain console, the other may have a shallow acquaintance with it. So my job is to help them do their job, remove the technical obstacle if you like. Or mix the show if no engineer present.
How is it possible to know everything? Well, it is impossible, but there are some tricks (albeit well known ones) that can help. First is, experience. If you do something for a long time, you’ve already met a number of scenarios/consoles, so you probably have a very good idea how things work. The second, which is not a trick, but wise planning, is to read manuals. I know it’s sounds boring. Actually it is not that boring.
At first it may seem like this is one of the most tedious things, but in my experience it is very interesting and even rewarding. Read every manual from cover to cover. You’ll forget many things, this is inevitable, but what you gain is an overall knowledge. What that mean is you’ll understand the building blocks, the workflows, the concept better, so even if you don’t know a specific function, you’ll have a pretty good idea where to look, what to search. So instead of standing there saying “I don’t know”, you’ll find the right thing in a minute.
This is why I really love to read manuals. Even before I meet a certain console (or any other equipment) I ferociously read every possible material about it. With this, even the first “date” goes much smoother. The same apply with any other thing, your DAW, plugins, etc.
The other thing is, often you’ll find hidden gems in some manuals. Some manufacturer goes way beyond basic functions and very eloquently describes even quite complicated audio related things, so you’ll end up with even more knowledge.
My advice is to read the manuals! Many spend countless hours to write it, and for a good reason: to help you! To teach you and guide you so after examining the manual you’ll be more prepared. So, RTFM!