I learnt to do that in elementary school for fun, I would personally do it by doing it concurrently fast enough that the bottleneck was my hand writing instead

I learnt to do that in elementary school for fun, I would personally do it by doing it concurrently fast enough that the bottleneck was my hand writing instead of the thought, so all I was actually doing in parallel was writing things I had already thought out, so I don't know how much this brings to the concurrency/parallelism conscious thought question.