I've found the Bic "orange" disposable mechanical pencils are really close to a really good #2 pencil--and they don't make dirt.
Being an architect from the dark ages - before CAD became mainstream, I have a number of old, brass barrel tech drafting pencils of various grades and lead thicknesses. I like the weight of these crafted instruments and prefer 0.3 mm and 0.7mm for chart plotting purposes. I must agree that sharpening pencils onboard is not the way to go.
I also have several German made K&E divider and compass sets, from my college days and some older collectable sets in leather cases. Very impressive weight and balance with some all brass and combination blued steel-brass, machine tooled components.
When working at the nav station with my archaic pencils, antique dividers and parallel rule, verse from The Rime of the Ancient Mariner echoes through my mind.