You can see both Lightning (the First one and the second after F.Forest). Both works with this setup (I tried another setup for the first one which was consistent but it didn't work for the Second Lightning, I don't know why).

You start your Flow timer (20.1sec) when "Ga" from "Gameboy" appears (look the clip) and it works until the "M" is 3/4 appeared. You have ~10 frames to hit. If you press A on your card combo (both works) at the right time and it doesn't make the glitch work -> you started your Flowtimer one or two frame too early/late or you didn't press A at the same time as your Flowtimer "beep".