I apprenticed under two very experienced groomers. Worked side by side with a 3rd.
There are schools that do teach grooming. Some are better than others. Personally I think apprenticing is the way to go.
What I liked:
Good Clients, problem solving, working without harsh supervision, control over my schedule, it was physical work with something to show for it, a well behaved client dog is just AWESOME, lots of exposure to dogs of all shapes, temperaments, health, and purposes. I loved working on well loved senior dogs.
What I disliked about it:
Dealing with the crazies - nothing is as sad as a dog owned by a crazy person who means well but is just insane. There was one lady who insisted her cavalier could not touch the ground, there was another lady who fed her dogs nothing but steamed rice and veggies, the lady who thought my shampoos were too harsh but Adam's flea shampoo was just fine, and then the couple who fed their dog nothing but lunchmeat and cheese. Ugh
Dealing with neglectful dog owners
Having to make the call of I can't see this dog til it's been to a vet to deal with X problem. I had someone bring me in a poodle once with an obviously broken leg. I had another person bring me a cocker spaniel with an ear infection so bad pus was coming out of his eyes. BARF.
Problem pooches who have never been acclimated to anything but owner wants out the door in under 2 hrs no matter how many dogs I have to do before theirs or what their appointment time was.
Being blamed for problems I had nothing to do with. I had a client tell me I clipper burned their dog. She came in and I did the groom again for free the next time. On her way out she mentioned that it was so bad before the dog had scabs all over her neck. As she said this I remembered that this lady had used a prong collar and I asked to see it, every single prong was sharp. UGH!! I remembered her taking the tags off of it when she picked up the dog the last time. UGHHHHH!! Still I had to give her the groom for free.
equipment and facility costs
Dealing with completely unreasonable people. No I will not groom your dog at 7pm on Christmas eve, nor will I just brush out your dog that is one giant dirty matt.
Lack of appreciation. I seriously spent 6 hrs once brushing, washing, drying and degorping a fully coated newfoundland that had took a swim in an open septic pond then rolled in a compost pile. They left me a $3 tip and told me my prices were too high.