Pairing tasks which require mental concentration with those that I could do while semi-conscious is the only effective form of multitasking that I can do. I’ve tried doing it the “grown up way” (i.e., several things at once without regard to what I’m about to share with you) but I didn’t get more tasks actually done, I just got more tasks started.
The Old Consensus was that if you were a multitasker you were a super-efficient individual who could do 23 things at one time with one arm tied behind your back and a baby clinging to one leg. I used to hear about all that multitaskers could do and think to myself that that’s what I wanted to be when I grew up.