I show them each card very slowly, there's really no need to go fast, the move is completely invisible even when done slowly. There is no reason for there to be any suspicion at this point. However, going fast will suggest that you're trying to cover up and as soon as they suspect that you might be doing something the reaction is going to be significantly weakened even if they don't actually see anything.
I go preety fast at the biddle trick. For me seems more fair than if I go too slow, because when you go pretty slow, they think you are doing a move. If you are going enough fast for them to see the cards and you are smooth it's just perfect.
I can't agree with this at all, in my opinion you're completely wrong. Spectators do not think you're doing a move if you go slowly, they think you have nothing to hide. Spectators generally expect sleights to be extremely fast moves, 'the hand is quicker than the eye' type stuff. They really aren't prepared for, and have no concept of, sleights that happen in a casual action. The steal in the biddle trick is completely invisible anyway, if they see you slowly count off the cards how could they possibly suspect a sleight? Whereas if you go quickly they're far more likely to think you're hiding something.
This applies to most other moves as well. Such as the Elmsely count, rushing it because you're worried they will see the same card twice is probably going to give it away, they're more likely to ask to see the cards again and suspect something isn't right. Slowly and smoothly and it appears that you're being very open and have nothing to hide, the audience will pick up on this and assume nothing is happening.