He Courtney; long time no see. I hope yo and those babies are doing well !
One thing about those cotton coats is you really need to keep up on the brushing with the pups until they grow out their adult coat. If not you have a holy mess on your hands. Its that puppy coat that can tangle and matt up. Especially under the pits and the chest areas and if you are putting clothes on her for long periods of time at this age, that only making it worse. I would suggest brushing her 3-4 times a week and its important that you get deep down all the way down to the skin not just the top coat. Sound like you are getting the matts ok but if you use a spray bottle with a little bit of conditioner (any) mixed with water it works wonders. Spray the matt and than work it around with your fingers breaking up the matt . Than using the tip of the comb drag the matt out. Make sure you hold that hair between what ever tool you are using and the skin. I also use a demitting tool (one without razors) it works very well. Use it the same way as Carmen described above.
One of my favorite grooming tools is a cat brush! I love it, they get down deep without poking the skin and drag out all that loose hair. You can find tips on grooming and pics of the tools that I use on my web site:
Grooming - Dawn's Yorkies
One think that I have found is that some of those leave in conditioners and deodorizers do more harm than good. Some will harden and clump and cause more damage to the hair than when you started. It easier to just bathe them and conditions leavings a smooth coat of the conditioner in to help with grooming process afterwards. And I always keep a spray bottle of water/conditioner on hand.