Thanks for your answer.
I agree with your thought, he goes to a wound care but they don't know what else could help him, not even the doctors, that's why I was asking about how to get rid of fibrin, because his fibrin gets really thick and not possible to clean it. He also feels much more pain when there is fibrin. It is complicated to deal with this condition, when nobody here in Brazil seems to have any idea of what to do.
My father has scleroderma for more than 15 years, then, he knows that fibrin makes the ulceration much harder to heal in his case.