I've found that by BFA does the foot up for both as well!! And sometimes there is no distinction between the 2. However, I have noticed that she will **** her head back before she bites with the foot up. It's very subtle and if I don't catch it, I may get bit. Although, I must say, Wanda rarely bites any more. And not nearly as hard as she use to. I haven't gotten blood drawn in awhile now lol.
The more work you do with him the better. I use trick training to take their mind off of negative things. I do High Five (sort of the step up lifted foot) And when she lifts her foot, I say High Five and put my palm up to her foor and give her a sunflower seed. It associates lifting her foot with a treat and it lessened her biting. If she attempts to bite I say No! and don't reward her.
Best of luck with your new fid! I love my zon and no doubt you will too. They are amazing birds!