Hi Birdlover1. How old is Echo? If he is young & still learning the step up command & being held on your arm, he will be timid about it. It sounds like you have a really good relationship with Echo already, so it shouldn't take long for him to feel secure & not worry about falling off when you hold him.
I don't bruise easily, but I had large purple bruises on my biceps & little nip places all up & down my arms from Roscoe, my youngest Catalina when I first got him. He was 4 1/2 months old & was just trying to steady himself, not trying to be mean. He was unsure of my arm skin moving under him & he would grab hold to steady himself. He also didn't know yet how to regulate his beak pressure & would hold tighter than he needed which caused the bruising. We both survived it & he learned pretty quick he was not going to fall of & hurt himself. Now he hangs off my arm on purpose since he is the clown of the flock.
As far as macaws on the shoulders, I am not a fan of it for me. I don't allow mine to get on my shoulder since I cannot see what they are doing, where their beak is in reference to my ears, eyes & nose. And I can't see their eyes to know what mood they may have just decided to change to which might not be the nice mood they were in when I first took them out for interaction. As was said, it is a personal choice & I for one choose not to allow it.
My newest macaw, Ruby Jewel was apparently allowed shoulder riding by her breeder before coming home 3 weeks ago. It didn't take but a few times of gently removing her & putting her back on my arm for her to understand I did not allow it. Crooking my arm in the goose shape did not work with her. She is large enough & I am small enough that all she had to do was hop up on my shoulder anyway. Her body is longer than my upper arm length!