I agree with the notion that no 2 snakes are the same. My bp won't eat inside her enclosure, she just gets scared and won't come out of a hide. She automatically goes into food mode as soon as she hits the floor of her box-o-death.
I tried feeding my young boa in a seperate container as well. It was too freaked out and didn't want to eat. I placed him back in his normal cage and offered the pinky again, and he took it without a problem.
Bottom line: do what works for you and your snake. Theres no real right answer to this question, except just to do what keeps them eating.
PS- Be carefule removing them after they eat if u feed in a seperate container. I saw a BP latch onto and constrict the hand of one of my co workers the other day. Wasn't pretty. We had to pour alcohol down the throat of the bp to get it to let go. This was a juvi bp that was about 2.5' long. I never thought a bp that size could cause the the amount of blood that was coming from the hand that it bit.