The raising of the arm thing is not used all the time, but is starting to come in more and more.
Steve from Sixth Sense told me that it might be used in my R class (forgotten whether it was or not). The thing Steve emphasised, and what gets a lot of people unstuck, is the panic reaction caused by the 'not knowing' where/when to stop. This is actually pretty good practice, as emergency stops are always a surprise.
I will repeat what I was told back when I did my test, and hopefully some of it might help you. If you have been told something different, and it’s working for you, disregard any of the below.
1)
Don't panic, very important. On a bike with decent brakes (almost all assessor bikes would be in this category) you have plenty of time to stop within the allowed braking distance without jamming on the brakes too hard. So remember, all you need to do is a controlled quickish stop, that's what they're looking for. Believe it or not, it helps thinking about it as a ‘controlled quick stop’ rather than an ‘EMERGENCY BRAKE OMGWTFBBQ’.
2)
Don't go too hard on the back brake. Depending on who your assessor is, a rear wheel chirp could land you a fail, or they could ask you to do another one. 2 rear wheel locks is usually a fail. Not to create paranoia, but remember, as you decelerate, your weight moves onto your feet, and more pressure will be transferred to your brake as a consequence.
3)
Prepare for your brake early. Preparation should include:
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straighten your arms (this limits the downward force on the accelerator from a rapid deceleration.
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Cover your brake and your clutch, be ready to apply a smooth, controlled brake.
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KEEP YOUR HEAD UP AND YOUR EYES ON THE HORIZON. I cannot stress this enough. If this is the only thing you remember, remember this. It helps, enormously.
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Be in a steady 3rd or 4th gear, depending on what bike you’re on. What I mean is don’t coast at 50Km/h in 5th/6th gear. Try and hold a medium amount of revs in 3rd or 4th rather than sitting at a gurgling amount of revs.
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Don’t pull in the clutch right away. I know this is a strange concept and there are differing opinions of this one, but again, I am repeating what I was told by someone who I have the utmost confidence in, and also what worked for me. The basic idea is that this helps you NOT lock up your back wheel, by keeping some drive to the back wheel during your braking maneuver. Pull in your clutch lever when you’re almost at a dead stop. The difference it makes is quite significant, and really helps you not lock up your back wheel. There are other forces in motion that help you stop quicker, but they are not important at this stage.
If back wheel locking up is not a concern for you, keep doing what you’re doing and forget about anything above. The biggest thing to remember is to do everything in a smooth controlled way. There should be no jerkiness in your actions.
I hope this helps, even a little bit

Good luck man, don’t get despondent, you’ll be out there in no time.
I recommend giving Steve at Sixth Sense a call (I have nothing to gain by plugging him) but he is seriously worth his weight in gold, can probably give you a quicker assessment time (he organizes it all for you, and hence can swap your time with another one of his students if he thinks you're more ready than they are) and insists on a lesson directly before your test.
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