The next thing that you can do is take a t-shirt and wear it around all day long. Later in the evening, take it off and place it in your boa's enclosure...near where he hides out the most. This will then help him to associate your scent with "home" and "security".
I read this somewhere, how true is it ? I am about to be getting a 5' BRB from someone and they barey handled her and they say she is very defensive. Alos how hard is it to tame down a older BRB ? is it possible ?