Like TStormdiver, I'm an instructor, so I'm demonstrating and practising drills all the time. From doing that, I'll definitely state that practice makes perfect. It takes a
lot of repetition to ingrain something into your muscle memory. You can only rely upon it,
if it is ingrained in your muscle memory as an instinctive reaction. Under stressful situations, where time is critical, the
last thing you want to do is have to think about your response.
The same is true, or more so, with technical diving. Again, like TStormdiver, I utilise a series of checks/rehearsals at the start of every dive. It's taught as a procedure by most technical agencies. I dive doubles a lot, even on recreational dives, so I'm constantly rehearsing and repeating drills whenever I can.
Repetition is the key. How much do you need to repeat something? Well... do it enough that you get completely bored and disinterested doing it. When it starts to happen by itself - and you find your attention on other things whilst carrying it out... then you are
half-way there.