It takes time to cure. Just keep at it with the soaks, cleaning, treatment and wrap. Some people have had good luck with using prid drawing salve too. I find that if a chicken is being reluctant putting a towel over her to contain her can help.
Once you get the scab off and the infection/core cleaned out you will still need to soak (20 minutes +), then clean, treat and wrap till it's fully healed. Depending on the extent of the infection and if you miss even a tiny bit of it can determine how long it takes to heal. Bumblefoot can be...