Welcome to YT!!
Well make sure to never brush a dry coat -- that pulls the coat & damages the coat & may hurt the yorkie too. I recommend a good spritzer -- I like Buddy Splash by Cloud Star
www.cloudstar.com -- you can buy their products a lot of places & someone on YT has it on their website too.
Buddy Splash is filled with natural herbs & oils. Smells great.
Also, make sure you use the right kind of brush for a yorkie. Some brushes are not made for their silky coats. I'm assuming you have a silky coat.
One of the best investments I ever made was in a Chris Christensen brush - I have 20mm Gold Pin brush. The dogs don't mind this brush at all - I rather think they like it.
http://www.chrissystems.com/brushes.htm
Good luck