It's not annoying when they can't do it. It's aggravating when they refuse to learn to do it and just want you to do the whole thing for them every single time.
I was a cashier at Walmart, once upon a time. The new guy i had to train refused to look at the corner of the screen to read the totals back to the customers. When I pointed it out that he should get in the habit of doing so his response was "I don't feel that i should have to do that."
I just... Walked away and got the supervisor to assign him a different trainer. I refuse to train someone above the age of 25 with that attitude.
I always verbally walk them through it. That helps them memorize the steps and if they insist I do it I can tell them to fuck off with a clean conscience. If they don't wanna help themselves then I won't either. I don't usually have a problem with this method.