I want to make some pose (PZ2) files to fit various hairs to other characters.

For example, if I spin the x y z and scale dials to fit (eg) a V3 hair to A3, how do I save the fit so that I can easily fit the hair to A3 again?

Does it make a difference if the hair is a CR2 or HR2 file?

What's the difference between saving a fit pose and a texture pose? (for example if I just want to apply a different texture mat to the hair.)

(I have searched for an answer but with words like 'hair' fit' and 'pose' I get so many results that I can't filter out what I want to know.)

Thanks in advance :)

I haven't tried it, but I would think you do it the same way you save a pose for a figure.  Open your Pose folder in the library, select the hair and follow the window instructions when you are saving.

Texture poses (MAT poses) are generated outside of poser, and still aren't really supported.  They're accepted as the standard now, but EF still doesn't really recognize that or support it themselves - textures and materials for EF content are loaded from the Materials room via materials collections.  MAT poses are kind of a legacy from before Poser actually had material collections, and materials were very awkward to work with.

As Acadia suggests, you ought to be able to save the pose and include scale transformations; select subset when you save the pose and only save the channels for the prop you want (the hair).