Could you post pictures of the swollen area?
I don't see any need to add essential oils to the Epsom salts bath. The Epsom salt itself will help reduce some of the swellings on the leg, kill most bacteria present unless it's a halophile, and most importantly soften the core to the point it can be excavated out.
Just continue to soak until the core (?), is soft, then take a pair of sterile tweezers, and scalpel, and try to peel away out at the plug, cutting any tissue if needed to get everything out. Once everything is out, apply an antibacterial ointment, or cream, like silver sulfadiazine. Wrap some gauze around the foot, and bandage with vet wrap. Change the bandage often, but wait until the hole is fairly healed or reinfection will occur.
Bumblefoot is often caused by excessive prolonged pressure to the dermal surfaces of their feet. Splinters on the roost, gravel in the run, wet bedding can also be predisposing factors. Correcting any environmental problems should be considered just as important as the treatment itself.
