I believe that patience is the key word. I am very fortunate to be able to do anything and everything with my female 13-year old Yellow Nape Hunter. I got her when she was just under 4 months, and she's always been quite "physical", wanting affection, wanting to be close.
When Sam came into our home 7 weeks ago, he was a shy 8-week old DYH boy, who actually lashed out at me when I needed to hand feed him for the first time. Well, he didn't know me from Adam, and he was simply afraid. By now he allows me to do just about everything with him and thoroughly enjoys head and neck scratches. I don't take them for granted, however, and don't know whether he will continue to enjoy all the handling as he gets older and will eventally mature.
I talked to Sam until I was blue in the face, but he listened, watched and learned to trust me. Not overnight....it took numerous weeks.
Hunter can be handled by everybody in the family, but Sam (so far) is only comfy with me.