What is the best thing to use on extremely rough and cracked fingers. it's real bad?

Heavy lubricant: Without playing favorites, "bag balm" (yes, it is a home remedy / homeopathic type answer) is a very thick, almost grease, that is intended for cow's udders, but works very well to protect (people) skin. You should also think how they got that way, since if you do not remove the problem, it will not resolve. Put on work gloves / cold weather gloves / protective gloves as needed; use gentle soaps.

See a doctor: It could be dry skin and it usually get worse during winter time. You could try otc lotion or cream. If it fail you should see a doctor.