Teaching my Rats their name ...?

I have six ratties and never seperated them to teach them their names and they all know exactly who is who, if I shout titch mitch doesn't come ect. everytime you give a treat say the name of who it is when you hold and stroke one say her name, when you hold the other say her name, they are very quick to learn, don't change their names later like I know someone on here keeps doing, it'll set your taming back, pick a name and stick to it, the more you say their names when you even just talk to them through the bars the faster it will be, another good one is a snack in the day, just stand near cage shout them out of their beds and when they come give it too them if one doesn't come then they get nothing if they are new and timid waft the treat near their hidey hole entrance but don't give it till they come right out to front of cage all the time keep calling their names eg come on ''bill'' come on ''ben''