How do I git gut at drawing hard surface objects such as cars,

Learn about perspective

Get the tools and practice technical drawing (aka drafting).

File: e79e93733a460d4bd530a34d5006c1fe.png (206KB, 1144x599px) Image search: [Google]

206KB, 1144x599px

same as with organic surfaces, ya collect up your visual library and apply construction in perspective to them. Fundies apply to all forms of shape languages.

Though, yeah, there's a lot more emphasis on mirroring, cause ya know... symmetry.
Pic related, a personal sketch with mirroring experience behind it.