When my mare injured her tendon sheath/annular ligament, I had to go through a few months of cold hosing. She's a major fidget and hates standing still for more than a few seconds so it was always tricky/messy!
I improvised with a gel filled ice pack from Marks & Spencer. It's intended for picnic bag use, but is a perfect size/shape with three sections of gel that you can freeze and then wrap around the leg and hold in place with a bandage.
I used to wrap this on and leave for 10-30mins (however long you want/need to) and when I took it off the pack was still pretty cold as was her leg.
Might be an idea for you? Plus, you can leave them munching on a hay net while the ice pack does it's stuff and you can muck out/do something else rather than waste loads of time standing holding a hosepipe- I found it so dull!
There is a horsey version which I've seen online with an attached velcro strap for convenience although it was about £20 and my ice pack from Markies was 99p!!