Maddcatter
Crowing
I sincerely appreciate this response, thank you for giving it.I'll second what @Eggcessive said. I have a hen whose had bumblefoot on one foot where I had to take out the kernel from both top and bottom. I will say that extracting it from the top is easier.
You can try this, it worked for me. With a fresh sharp scalpel, incise a small "x" right on top of the "bubble" in between the toes. The skin is very thin and you don't need to press very hard with the scalpel.
(Have some cloth or paper towel under the foot to catch the blood or do it over a sink)
Then use your fingers (wear surgeons gloves) to squeeze the sides of the bubble. If you're lucky, the kernel will pop right out with some pus. Flush the cavity with saline solution and then apply pressure to stop any bleeding.
I highly recommend applying an antibiotic cream with mupirocin if you can get it.
The hen I operate on was a "rescue" and she had terrible bumblefoot her first year. It's harder to get rid of the more established it gets, so I got a lot of experience operating on her. But I've noticed a lot more healing since using this cream. It's more effective against staph bacteria than other antibiotics.
Perhaps it's not well established and you might get it all out, but don't fret too much if it comes back. Just repeat the process. While you want to try to take out as much of the infection as possible, in my experience it's been more effective and easier on me and my hen to do successive "cleanings" than trying to dig for kernels (especially when they are the little stringy ones) and traumatizing the hen.
Good luck!