I'm happy to report that things have resolved themselves.
First of all, yes I was applying poultice with a bag over my hand because I am apparently unable to remember to purchase latex gloves.
Fortunately my mother reads this blog, and took matters into her own hands. I am now the proud owner of a brand-new box of 200 gloves, shipped in fresh from Colorado.
Sam's life has also improved since last week.
Day 1: treated with cold hosing, poultice, wrap, and 2 grams of bute (I forgot to mention that before). Bute is a painkiller and anti-inflammatory, like aspirin. It's good stuff.
Day 2: Looking better, but still pretty swollen. By then, the swelling had moved down and around his lower leg so I was glad I'd already started treating those areas. I repeated cold hosing, poultice, and bute but did not wrap him. I'd have preferred to keep him wrapped one more day, but it was a practicality and scheduling issue.
Day 3: Suddenly much better! A residual bump from the point of impact remained on his inner leg, but the rest of the swelling was 90% gone. Hooray! I did more cold hosing, but nothing else.
Look at that pretty, slender, non-cankley leg. Bueno.
Once again, poultice (and cold hosing, wrapping, bute) wins over evil. Viva la mud!
Horse dorks: Are you poultice-believers or do you prefer furacin? Do you cold hose or ice boot? Wrap or not?