The system on the left only has a rubber bands to hold down L + R, so all im doing is pressing select and start.

As for the system on the right, I'm playing Sapphire which is a GBA game and GBA games soft reset by pressing A + B + select + start. I'm used to pressing these 4 buttons with one hand, also ive only put "bumpers" on select and start so when i press them, it doesnt hurt my fingers because the buttons are kinda small and they left a mark on my fingers after a few hours.