You might be a particularly good groomer though and I mean that. I have had a couple of different breeds and no matter where they go they just get shaved. If you ask, leave the ears, leave the tail, they look like a poor representation of a dog when they come back.
I do understand your problem with the elderly but having had a hairy lad at 15 and needed the help to remove some coat for the summer, I was aware and asked for whatever to be taken off sitting down and around the bum area. I just can't work the clippers to do the job and I needed some help from a professional. So I do think that is unfair a point though I was aware what they could do was limited. It wasn't for appearance, it was for him.
Start them young depends on the breed, because a lot of coats are manageable by the owners until a certain age. Also neutered dogs in particular breeds tend to grow heavier coarser coats if they are neutered later.
If the coat is too hard to brush out, save yourself the aggro and tell them it will grow back! Good on you for trying.
I am sure a lot of dentists have the same wishes you have!