@rowuk My experience with good techs is very much like yours. I have not built a trumpet from scratch, however. I knew a particularly skilled and generous instrument repairman/fabricator who allowed me to not only observe, but also on occasion participate in repairing and servicing various instruments, and he at times guided me in working on my own instruments, for which I am forever humbly grateful.
The genetic wiring in my brain has always enabled me to excel at all things mechanical, and I have always been willing to share my knowledge with others without concern that someone would steal business from me or outdo me in other ways, because I knew it would be very difficult at best for them to do so. If someone is better than I am at something, that means that there is room for my improvement, and it also means that they deserve the patronage of those looking for expertise.
I have observed that those who jealously guard their "secrets" may have shortcomings that they do not want others to discover and are uncomfortable having others looking over their shoulder.
On balance, I also feel that there are those who have no innate ability in certain things and should not be encouraged to pursue them, as disaster surely awaits them.
