This could become a long answer, but I will try to keep it brief.
1. Complete assessment of neurovascular status: have they had ABI's and TBI's, this will indicate whether debridement of slough is viable. If they have critical limb ischaemia it is best left to the vascular surgeon to revascularise or amputate.
2. If vessels are patent, I would then check the cause: could more pressure from foowear be prevention healing: we now go to a CAM walker or air walker to completely off load the forefoot pressure, otherwise the open toed post op shoe could be a temporary option.
3. Dressings for this type of would wound involve a desloughing agent: a hydrogel such as intrasite gel or solosite gel(smith & nephew) would break this down if you can't debride it with a scalpel. We would then apply an absorbing dressing such as a foam (allevyn or biatain) to absorb exudate and protect the area. Secure with hypafix tape or whatever the patient is not allergic to.
4. Educate the patient until they can repeat back what you have told them and have it all written down as they can show carers, nurses, etc to confirm the treatment required.
5. If not already done, swab the wound and check for microbes which could delay healing even if the wound is not showing signs of clinical infection, it could be colonised.
This is the tip of the iceberg, but it's important to communicate with all parties involved to ensure best practice and prevent the amputation.
The international consensus on the diabetic foot is a great reference to use for supporting what you are doing and why.