For ADHD brain, the timer built into the toothbrush makes all the difference. Sometimes that 30 second interval feels like five seconds, and sometimes I could swear it's been five minutes and I start wondering if it's broken. Nope, that's just ADHD time blindness. I almost certainly never brushed for anywhere close to long enough prior to my electric toothbrush.
My electric vibrates the timer.. I just brush each quarter of my mouth for each timer period. The vibration is annoying, but it's a routine that works for me.