I use Yorkie Splash, a shampoo made specifically for Yorkshire Terrier coats. It's hand made with all natural organic ingredients with a ph over 9. I think it's about $8.00 a bottle but a little goes a long way. You can google it for more info. I can bathe Sophie every week with it and it doesn't dry her skin or coat out. It makes her feel fabulous and smells great. Even my groomer loves it and wanted to know if it was available for other breeds, too.
Jackie & my 
Sophie 