I have these questions:
1) What determines the softness/smoothness of hair? I've read
somewhere that it's the oil produced by the sebaceous glands (the more
sebum produced, the softer the hair). Is this true or is there more to
it?

2) I noticed that my eye brow hair is much smoother and softer (my
ideal) than my head hair. Why? I have very dry curly hair. I want to
make my hair naturally soft, smooth and possible straight. And I don't
want to take special hair treatments. What should I do?