I think all mk4 drivers should try this at least once even if your discs dont need cleaning.
The button is also your emergency brake, in the unlikely event of not being able to use the foot brake.(eg complete hydraulic failure, maybe the brake pedal siezing or dropping off, or your leg trapped, or some sort of medical emergency.) Its not as obvious as using a conventional handbrake lever , so familiarity with the system makes it more likely you , or a front seat passenger (even non drivers who have been 'initiated') will react more quickly and be able to stop the car in an emergency.
You just need to pull the button up with a finger ,and keep it pulled up. . For a second or two the braking affect is quite slight. Maybe to give the driver time to react if a curious passenger unexpectedly pulls on the switch. But braking quickly becomes more powerful perhaps reaching a more rapid stop than you are comfortable with. If so just release the switch a bit. With a bit of practice you can actually control the rate of braking by easing off on the switch slightly which could help you come to a more controlled stop - if you have room. But not a 'skill' that has any practical use in normal driving.
It also gives reassurance that the car has effective independent duplication of its braking systems . In the event of hydraulic failure or non function of the foot pedal, the electrical systems would still be able to apply either partial hydraulic braking, or if there are no hydraulics at all it can still apply the powerful electric rear parking brakes . In the event of complete electrical failure the hydraulic brakes should still be working, albeit without (electric) power assistance.
In the most unlikely even of both systems failing at the same time I think you must accept your fate is sealed

I really like an electric handbrake. Especially coupled with the cars 'brake hold' function. But no more 'handbrake turns'
