Do you use detangling spray? I use that on Katie Scarlett when she has a tangle and it works great. I usually spray the knot and pull it apart with my fingers. Then I slowly try to brush it out without pulling. We have used 2 detanglers:
PetHead and Yorkie Splash & Shine kind,
Yorkie Sheen. We like both of them. I want to try that Chris Christensen
Ice on Ice kind next. Detangler really helps us.