I am in the same boat, and am keen to do what I can to tame Dennis-Sama to the point he doesn't fear my hand.
I did find this Video by Erin at Erin`s Animals which has some good advise.
https://www.youtube.com/watch?v=u7hf9d6TF_A
Keep the box high enough so he they cant escape they will eventually calm down and start to climb on you, do it regularly enough they should become accustomed.
Dennis-Sama was quite happily climbing up my arm to escape, even to the point he sat on my hand for a while assessing what to do.