I am dealing with the tail end of having two hens with bumble foot and I will tell you what worked wonders for me. First, I got Tricide-Neo powder from this place:
https://www.pondrx.com/product.php?productid=16166 and soaked the hens foot in it every day to every other day as it began to heal. I did not have to open them except for one that was on the very front of the toes, between them, and when I did puss came oozing out. Once I soaked their feet for about 5 to 10 minutes, I dried their foot off, then slathered the area with a generous dollop of triple antibiotic ointment, put a small piece of cotton on that, then wrap the cotton ball onto the foot with a strip of vet wrap, but not too tightly done, so the cotton ball keeps the triple antibiotic ointment on the wound so it can soak in and further fight the infection. You have to be diligent with the care and cleanliness but the tricide-neo, while for koa fish, does work wonders, and often times without surgery, other than initially opening the hole or pulling the little scabby plug.
Tricide-neo works by soaking into the site and destroying the bacteria and bad stuff, it is often used on other raptors in aviary rescue places with great success too.
Be VERY careful with PenG as penicillin can cause major damage and/or death should you not get the dose exactly right or inject it in the wrong area. Our vet put my little hen who had it the worst on amoxicillin and we looked up the dose after weighing her and i got her to eat it by putting it over scrambled eggs or on a few pieces of broken day old bread and it would soak up the liquid then she would gobble it all down.
Great idea to give your hen scrambled eggs or anything else that may give her extra energy. I actually went to my small animal vet and discussed the above and she gave me the green light, as she does not like to open any animals body unless it is absolutely necessary. This has worked wonders. I too do not like to open anything, as it can, it not cleaned properly or done right, cause more damage than good.
Good luck. One note, before cutting and cleaning the foot, I would soak first, this will soften the skin and soften the tissue or plug that you need to get out of there first, lessening the pain and discomfort.