It took me two days, lots of careful combing, and bit of Main-N-Tail Detangler. After the first day I had managed to start to undo the braid and get the bottom half of her tail detangled. I banded the bottom half and pulled it up. I started off day two with this:

I sprayed the sections I was going to work on. Then groom the rest of her for a bit as I waited for it to dry. Then I held the tail and pull a few hairs out from the burrs with a comb, a few strands at a time. Finally an hour later I had this:
Now why would I go though all this when it is totally impractical and I could just thin the whole thing down to a normal looking tail? Well who hasn't wanted a real life "My Little Pony?" I have and so has my mom. It is her pony. So even though it is a major pain sometimes, I keep her tail looking like this just so I can take it down and let my mother enjoy looking at this tail.

Today I have to wash her tail, which is another chore. Once I get it all washed and conditioned it goes back to the braid and bagged. Luckily the best tail care you can do is handle the tail very little.
I took one last photo of the braid before I put it up just to see how long it really is.