How do I get a breathy vocal sound like Julia Jacklin's on "The Big Why"?

Use a large-diaphragm condenser mic (like a Neumann U87) six to eight inches from your mouth, angled slightly off-axis to reduce sibilance and add warmth via proximity effect. Always use a pop filter to handle the extra air. In the mix, add a gentle high-shelf boost around 8-10 kHz to exaggerate the breathiness.