I remember the days of thatching.....
If really wet i would use a sweat scraper to get the worst of the water off and use either my waffle weave or fleecy cooler (waffle if colder).
I also have a weatherbeeta wick dri cooler which is great for drying off in the summer or for a very woolly pony thats not usually rugged.
I remember the days of thatching.....