I do agree that flea shampoo dries out the skin and it's not recommended to use it on regular basis. It's a very agressive shampoo. I'm a groomer myself. I don't use slicker coz you'll break the coat. If you ever go to dog show, nobody ever uses slicker to their yorkshire. They only use pin brush (with no point at the end)
Many groomers know nothing when it comes to Yorkshire standard and how to keep those coat show. They usually advice you to shave the hair. I'm myself is a big fun of show coat hair. I attend to many dog shows to get some useful information. I bet that this groomer knows nothing about how to grow a dog show coat. You'll never achieve perfect show coat if you use slicker. This is a very bad idea
onless if you want to break the hair
I post pics of Kenzo. You can see his pics in order to have some idea of him