Pity, with all the other creativity stuff they'll play autonomously, they couldn't have come up with something in the game! Although, mechanical is one of the fastest skills to learn, I find (at least in the early stages, a sim reading up on mechanical finishes that level faster than a sim getting the same level of charisma.) What one really needs is a clogged toilet they can never unclog - just to learn on!
That may be true for shy sims, but outgoing sims, on the other hand, will learn charisma faster. Mechanical skill is not connected to any personality streaks, so everyone learns it at the same speed regardless of personality, just like cooking. All other skills can be slowed down or sped up according to personality.
Author