I don't have a grey, but my chestnut often has this problem. It gets quite cold here so I've adopted some useful methods I am willing to share.
First, gather up all your tail. Then, slowly, begin picking very small sections to get all the knots out. Do this until the entire tail is knot-free. Finally, starting from the bottom of the tail, GENTLY brush the ends, rising upward as you go.
If there is any major staining, use SOME Cowboy Magic on your hands afterward and gently go through the tail. Too much Cowboy Magic means added silicone into the hair which makes everything more difficult. This also damages and suffocates the hair itself.
If possible, you could use warm water when washing the tail and dry it with a towel afterward? I have never done this, but I hear it is a popular method of tail cleaning during particularly cold winters.
If you know how to plait correctly, that would be a good idea. However, do not leave it in for extended periods of time as the horse will start rubbing her bum on things to itch and end up damaging the tail.
Sorry Marcie i didn't fully elaborate. I clean his tail by using Silver shampoo first which gets rid of all the stains and brings out the white and then proceed to put it in the tail bag wet. It is also cold where i live but i just boil some water and mix with cold.
Me too! It was -50 last week and my grey mares tail is so dirty. I was asking myself the same question. Dunking her tail in a bucket of water is not an option as either her tail or my hands would freeze and break off! Lol.
If your horse is supper quiet you can dunk it in a bucket of warm water to wash it out, then dry it quickly with a hairdryer on the heat setting. Unfortunately most horses freak out at the sound it makes.