For some reason (unknown to me) some players refuse to allow themselves to play the trumpet. I've seen this hundreds of times over many years.
When we learn to use a fork someone shows us how to hold it. For several days / weeks we concentrate on the process. And after a small level of mastery we let go of the "DETAILS" and simply use the fork. We repeat this same process thousands of times during our lives. The very first attempt at a physical action requires thought. However after doing that action many times muscle memory can and should take over.
We all know people who can't swim. Swimming is taught sometimes in a series of steps. (Like trumpet playing) You first get to the piont where you can float. Then a glide action is learned. This is using the legs as you float. And finally the arms are added to the glide and you are swimming. However some people don't learn to swim (even after taking lessons). They never allow the muscle memory to take over. Because there is a fear of something happenning. The fear adds tension which not only throws the muscle memory for a loss it also causes you to sink. This person has to overcome the fear to be able to swim.
For many people trumpet playing has some aspects that bring up small concerns. Will I play the right note, is a concern from day 1. As the ensemble we play in gets more experienced there are more concerns. Tonguing, range, endurance, tone ....... It is these concerns that are preventing you from allowing muscle memory from taking over.
Learning how to set a proper embouchure for some people happens on the first lesson. Others learn this after a few months and still others after a few years. These people have had months and sometimes years of playing concerns. It is NOT the method book that is causing the confusion. It is the months and years of being worried about what will come out of the horn.
In the case of swimming the fear is of drowning. That is a REAL possibility. In the case of trumpet playing the fears are mental. A wrong note or faulty articulation will NOT cause a death. Every player has made playing mistakes. Learn to let them go. Being uptight causes these mistakes. And they build on each other. The first note is missed. This sets the mind to question why . Now you are preventing the years of practice from working for you.
How were method books intended to be used. Well I've written 2 so I will answer based on these. It is a guide. I NEVER wanted or intended for anyone to concentrate on each line of text as they play. Certainly if you are changing some aspect of your playing you may concentrate on an IDEA for a couple of days. But then you have to LET GO & MOVE ON. There can be no real progress until then.
You are right in stating that teachers were not hiding things. We are not hiding anything. But many times the student may bring some preconceived idea to the lesson. Problems with learning the ease of playing are not much different in person than they are when reading a lesson. The lesson will not help much until the student is ready to accept the idea, work on the idea and then let go and use it.
'Pops' (Clint McLaughlin)