I use multiple products.
I'm a big fan of Chris Christensen, Ice on Ice. But I also recently discovered a product called Naked Care (just google it). I used it today - for the first time really - and Indy's coat is so incredibly soft, I cannot imagine why I did not use it before. As a Tri, his coat tends to be a little more coarse than Bacca's. Now I run my hands down his coat and he feels great!
Of course, this was a mix of CC Show Offi, CC Ice on Ice and Naked Care. And about 1 hour of brushing. All in combo got all the mats out of his butt and ears. So I'm not sure which product was the miracle.