A huge solid mat my mom's horse's tail.
Take the mat and spray generously with WD-40
With a hoof pick comb or brush start working the mat out from the end of the hair on up
Keep working at it don't be afraid if some hair falls out. It's ok.
About 20 minutes of work later...
A mat free tail!
Look! No more mats!
To get the WD-40 out wash the tail first with diluted dawn dish soap then with mane and tail shampoo. Then apply mane and tail conditioner and let it stay in. Braid tail to keep it from mating again
A messy but braided tail.
It still drags the ground even after we braided it!