I use the outside edge of my right foot to blip the throttle, when the rest of my right foot is on the brake pedal. I've done this for 100 years, in every manual vehicle I own and doing this daily in normal every day driving scenarios. It is just 2nd nature to me. I do this also on motorcycles. It is much easier on motorcycles (I use my palm and index finger on the throttle and my last 3 fingers on the front brake lever ... very easy and smooth).
If you're not doing it, of course it is not necessary. But it does allow you to brake slightly and smoothly and let the engine provide some of the braking as well. It just takes some time to get used to, so that you don't push / pulse the brakes when your foot's edge is poking the throttle. And some time to get to the point that you get as much rev as you want from the throttle when you're trying to be smooth on the brake pedal.
Like I said, not necessary, but it is 2nd nature to me. In my truck I get a lot of attention doing this. Because the truck is LAF, and sounds seriously like a big rig. So when I'm in traffic and we're all slowing down and I blip the throttle even while braking ... those who put 2 and 2 together (hey he's braking AND revving simultaneously) sometimes give me a look like, dayim...
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View my fuel log 2020 Mirage ES 1.2 manual: 42.4 mpg (US) ... 18.0 km/L ... 5.5 L/100 km ... 51.0 mpg (Imp)