My husband is not diabetic according to the doctors, but is with the home tests, however, he had an ulcer on his foot for almost twelve months, it was horrid, and so difficult to treat on the sole of his foot. Tried numerous things, including Manuka honey, and also some Dermawound.
http://www.progressivedoctors.com/wound-care.h tml
The Dermawound did reduce the size of the 'hole' by about 50%, and cleared up a smaller ulcer on his other foot. We did get a full refund as it was guaranteed to give results. We then got some Youki cream, which reduced it again by another 50% of the remaining size.
http://www.winhealth.co.uk/Youki.htm
and finally, dont laugh this is absolutely true, my husband decided, in his wisdom to use superglue, and within a week it had gone. (I wouldnt recommend superglue though, he is just stupid, and as he has raynauds he cant feel his feet anyway, so any stinging from the glue he didnt know about)
I think when the skin starts to heal and go hard, using a pumice stone or similar to remove dead skin really helps.