You can use an underlay if you know you’re going to be sketching iterations of the same design & angle (helpful for cars where you don’t want to keep filling in wheels, but the flip side of that is if you don’t constantly draw wheels you’ll never be good at drawing ellipses).
Depending on what I’m sketching I like to sometimes use a 20% gray marker to start. It lets me be really broad and loose and see if the thing in my head makes any sense and put down some perspective guidelines before jumping back to ball point. The light gray can be quickly taken out in photoshop with a quick levels tweak if I need to.