The math is not trivial enough to do with pen and paper.
There's nothing stopping you from applying the key derivation algo step by step using a calculator, or an offline computer.
It would make for an insightful, albeit time-consuming, experiment.
It doesn’t matter how easy/simple it is to derive a public key from a private key. What matters is how easy it is to go in the opposite direction. As your link shows, it’s not that hard to do elliptic curve multiplication by hand, and there’s no need for it to be hard/complex.