Rather than making hairs from scratch, using pre-made assets would jump start the process. Facial Hair Toolkit offers hair assets to be shrink-wrapped onto your characters with various controls such as density, length, shape. At the same time, it streamline the process of hair cards creation and hair texture baking.

take a look at the video demo above for introduction or documentation page for detailed written guide.
here is a quick guide on how to export Geometry Node Hair to Unreal Engine 5

Various premade hair assets:
Hairstyle
Hair Element

Eyebrow

Beard

Draw Eyelash

Combine Hairs

Save Hair

Hair Presets, use existing ones or make your own

Hair Cards Creation

Custom Hair Mesh

Hair Texture Baking

all eyebrows

all beard

haircuts

hair elements

update 2.2.1:

minor bug fix: when saved hair is not given a name, it would cause import error.

added an open folder button to jump into the relevant asset folder.

update 2.2:

added: custom hair mesh.

in addition to generated hair cards, now you can also use custom mesh to distribute on hair curves. one useful case is that you can manually place several hair cards together to form hair volume instead of flat shape and distribute it on curves. take a look at doc page section 3-5 for more details.