First, to avoid confusion with HILD (hypnotic Induction of LD), I suggest Hagarth's brilliant technique be called FILD (Finger Induction of Lucidity). Second I propose a better RC, because the one he uses (breathing through pinched nose) involves moving the body, which could pull you back from a LD. HERE IS THE NEW RC, WHICH CAN BE USED AS A REGULAR RC WITH ANY INDUCTION METHOD:

Take any double digit number and try to double it. For example, take 37 and try to double it = 74. Since logic and analytical ability are absent in a dream, if you can't do it, you either can't do basic math or you're dreaming. The other variation is to halve any even number. For example, take 96 and divide it by 2 = 48.

One big advantage of this RC is you can do it anywhere without attracting attention. The other big advantage is that if you can't do basic math, it will TEACH you to do basic math, which can be a big help in surviving in our modern world. Once you start practice basic doubling and halving, you will find this a very simple and easy RC. Good luck!