I think I will offer to wash and style a friend's natural hair when I'm white.
Why are you offering to wash her hair?
I want to try styling an Afro because I don't have one.
While your reasons are kind of selfish, it is okay to offer to do favors that you benefit from. You should always get permission before you touch someone elses body and not pressure them into your ideas.
When I was growing up, I really liked seeing Afro hair. My parents wouldn't let me try and get such a hairstyle or afford to style it since mine isn't curly.
It is ok to be curious about peoples hair textures. It is wrong to pressure people into letting you touch it or attempt to style it like they are your pet.