Think snake oil and travelling salesman and you won’t go far wrong. Whilst the exception may prove the rule, dressage method is a deliberately one size fits all attempt (usually successful at least for a fad period) to prey on the insecurity and wallets of those still convinced that dressage is a sport (thus thinking they may achieve success by actually riding better). Look for the book and the video and there is method not far behind.
The best methods which produce success are then declared cruel and foreign (in no particular order), normally in the promotion of another equally uniform and expensive method of the detractor ( with accompanying video and interview in the equestrian press). Thus rollkur goes from highly successful method of training champions to engage to cruel hyperflexion, by judicious use of video clips.
Horses are different and may even need special and individual treatment, and even the least observant THF can spot a method a mile off – especially when the cheques start flowing. Advice from an experienced THF – look for a trainer who actually seems to give a damn, doesn’t spend their time either on the mobile to a much more important client whilst teaching the Funded or (even worse) convincing the Funded :
that they are useless riders and/or
that their horse would be much better ridden by another client(or them) and/or
that the combination would be fantastic with the benefit of a lot more (expensive) lessons and/or
that the Funded would do much better on a horse that just happens to be in the nearby box at a bargain price (this is about the worst as the technique – but not usually the horse – often works)
A good and helpful, supportive trainer who cares is to the THF worth their weight in gold. More depression has been caused by trainers in dressage than almost any other field of human endeavour. The opportunities for undermining the confidence of those genuinely seeking help and support are legion and the temptation to be Svengali is often too strong to resist.
thehorsefunder 
I sense a person close to the end of his tether! However, you must have come across the sort of trainer I do know about, but luckily do not really know. I guess, find the one who empathises ,who isn’t driving a ferrari/lambo/porsche, who will work with not against, who improves confidence as well as seat , and who really tries to find answers. However not every aspirant will make their Grand Prix dream come true -some just don’t have what it takes, and no amount spent on lessons will be able to change that. The pupil needs to be realistic, and I have seen some who aren’t, it’s always the horse’s or the trainer’s fault, never theirs. What a nice world a perfect one would be!