Soak the feet in some warm soapy water to help get some more of the mud/debris out of the feathers, legs and folds of the feet. Anti-bacterial soap (like Dial) or dish liquid (like Dawn) works well. Gently scrub the legs with a soft brush, trying to get in the nooks and crannies.
The feet look inflamed, so after he's cleaned up, soak his feet/legs in some epsom salts, betadine, Chlorhexidine or something similar to help with healing and hopefully to reduce inflammation. For any cuts/wounds that you see, apply some triple antibiotic ointment or Vetericyn. He would most like benefit from a daily soaking of healing solution and re-application of ointment for several days. Drying the feet the best you can and keeping him dry bedding.
It looks like he may have some scaly leg mites as well, I see some raised scales. For those, while your cleaning him up, make the water deep enough to soak the legs too, then where you can, gently brush the scales as well to help loosen any mite debris. Coconut oil, A+D ointment, Vaseline or similar applied to the legs will help smother the mites. SLM can be hard to battle, especially on feathered feet/legs, so apply your choice of oil/ointment daily to the scales as well.
To give him a boost, provide him with some poultry vitamins a couple of times a week and offer him some extra protein like egg, tuna, mackerel or meat.
Keep us posted.
