Treating an Abscess - homemade soaking boot

It's that time of year again.  Cupid and I had several great lessons, and then last week as soon as I asked him to trot it was clear he was lame.  It came on suddenly and there weren't any other symptoms, looked like an abscess.  I packed his foot with ichthammol and wrapped it, with plans to get some epsom salt and soak it.

Last time I soaked Cupid's foot I had him stand in a flat rubber feed tub.  It worked okay, but he did pick his feet up out of it a few times and made a bit of a mess sloshing water around.  At Walgreens next to the epsom salt I saw something I thought might make a handy makeshift soaking boot: a "Reusable Waterproof Cast & Wound Protector."  It is a heavy duty plastic sleeve with a rubber top, made to go over a person's leg cast but turns out it works quite well as a horse soaking boot!

I put the epsom salt in the "boot."  Then I put his hoof through the hole in the top and pulled it up on his leg, where the rubber top sealed nicely just over his knee.  I spotted a watering can next to the hose, and used that to pour warm water in.  Cupid was very good and stood still while I did it.  (He was eating his grain, so that may have helped!)  I left the boot on for almost 20 minutes, and it stayed on nicely.  Cupid was good, he shifted around a little but was mostly content to stand there and eat with the boot on.

Cupid was moving better by the next day, but I haven't seen any drainage so we're going to keep taking it easy and keep packing and maybe soaking the foot.