In addition to doors, you can also level up mechanics with a crowbar by popping crates open. It’s much faster than with doors, too, as you only need to 'e’xamine instead of 'a’pplying then selecting the crate. Use a makeshift crowbar for maximum effect. This could level up mechanics to 2 easily, if you could find at least a dozen crates to work with, that is. Past that, use vehicles.
For electricitronics levels 3-6, crafting and deconstructing directional antennas is the fastest way to level the skill outside of books itself. This does require the book Amateur Radio for Enthusiasts, but this technique does make a nice stopgap in-between that level gap.
