I have to again mention Germany also. I was blessed with an outstanding farrier for close to 15 years. He was a master farrier, so was his father and grandfather. His journeyman had no intentions of becoming a master, was happy as a clam with his boss. Those two did between 800 and 1000 horses a month, from race horses to jumpers and dressage horses in and around Bremen, prime Hanoverian country. He was doing a barefoot trim pretty darn close to a now known as wild horse trim long before Jaime Jackson came in the picture.
I never had a sore horse with him, he wanted to keep shoes off whenever possible, but shod when necessary. He explained everything he did, showed hubby how to do touch ups when needed, was always punctual and never ever rough with a horse. When we moved south about 600 miles, he still came, every six weeks, always on time. I couldn't convince him to come to Italy when I moved there, unfortunately.
When leaving Germany, there were two or three hoof care specialist schools in place, with owner courses and professional school. The pro's had to do school( theory) and parallel to that, apprentice with a certified trimmer, get a certain amount of apprentice hours, would get rated by the certified trimmer, before they could do the final test. These schools were approved by the government, and trimmers couldn't shoe a horse with metal and nails. Glue one and booting was allowed.
This would guarantee the horse owner a certain standard of knowledge, just as a certified farrier who went through the apprentice program.
It takes some of the guess work out of finding a good farrier/ trimmer.