Everyone gave good advice so far. I'm sorry you're not seeing the sweet side of tiels right now. I do agree that in order to bring in a second, your first one must be tame or you'll end up with two wild tiels. Start leaving the cage door open for them and do it everyday around the same time. Tiels like things to be predictible in order for them to feel safe and comfortable. I've never used clickers but have heard they are effective to a certain extent so you can give it a try. I think you'd have to do the trainings seperate and take the tamest out for lessons first. You mentioned the female bites and almost drew blood. Almost doesn't count. Females fake bite and hiss ALOT even when extremly tame so the key is not to react. I know it might be slightly painful at first but once they realize that biting doesn't make you go away they will stop. Also, you didn't metion whether they are clipped or not. If not, then I recommend clipping them atleast for now until they are tame. Let us know how it goes.