This may sound strange, but here goes.

When I was waiting at the groomer, a woman was complaining about your issue. The groomer recommended a CAT comb as she felt they were more effective for mats. Try using a wide toothed comb (or brush with teeth) and hold the fur closest to the skin with your fingers to reduce pulling. Start at the end and work your way up. If your dog has a thick undercoat, an undercoat comb with two sets of teeth at different lengths may work better. If that's not successful, a mat (or razor) comb is another option. Remember to hold the base of the dog's fur and skin to reduce pulling. She doesn't recommend scissors because it's so easy to cut skin.

Hope this helps!

Huh, I didn't know that was called a cat brush. That is the brush that I use for the schnauzer and the only one he tolerates. I will do as you say re: holding hair to see if I can take the stuff off. He's such a happy dog running like the wind but oh how we pay afterwards, ha

Checkout the horse supplies at your pet store, or find a feed store, and try a detangler for horse mane and tail. No matter what you use, those seeds won't be easy to brush out but the detangle product will definitely help. I had to clean a pony's tail that hadn't been touched in months and it was full of mud, manure and shavings. Detangler and lots of warm water did the trick.