Well, I had the same problem! (Except I don't get enough time to brush him everyday).
How did I fix it you ask?
I bought some tail & mane showing spray from the horse shop and I spray it in his tail before brushing it, the brush goes straight through his tail and the spray gives it a nice shine!
I'm not sure on what the spray is called but if you ask the staff at what ever place you buy your tack, brushes, horse clothing, wormers etc from I'm sure they can help you!
Here's a photo of his mane when we got him, it was hard to brush out without the spray, then we got the spray and it worked like an angel! DSCF0777.jpg