Try practicing with air soft of the same model you carry. One of those little pellets is a great reminder of how you blew it. WEAR SAFETY GLASSES!!!
That really won’t help in this case, as you are not practicing your quick draw or shooting someone, but *acting*, trying to figure out *realistically* the time intervals when you can use your weapon when faced off with an armed mugger.
Even both being armed with bananas (the Glock .40 banana), will work in this case.
The emphasis is where the mugger is focused, what he is paying attention to, when he is vulnerable to you, how much time to get your banana, make sure it is off safe, etc.
You are trying to tactically calculate fractions of a second for advantage. You are looking for an opening, like a boxer.