Hello,
I had the same problem with my youngest dragon, she was given to me by a friend who couldn't handle her anymore due to her being extremely skittish and "aggressive".
She was extremely skittish at first but what you need to do is show them that they can trust you, do like Tracie said hold them at night with a soft blankie to get them used to your scent. I used a old soft T shirt to I wore a lot to wrap her up in and that helped her with getting used to my scent.
It took her much longer to get used to me because she was held only once in the few months my friend had her.
But Fast forward 3 months or so and she's a total sweetheart and snugglebug.
View media item 60844 finally starting to tolerate blankets in her second week.
View media item 60959 she was super skittish at first and hid in her log all day.
View media item 60452View media item 60662now she's much more used to handling and is much less skittish now.
it just takes time with these things.