I see hair fit poses to make hairs fit charactors that they werent originally intended for...but how do you actually make one ...I would like to learn to do this for myself instead of relying on the generosity of others (Thank you to those who have created them)

I don't have any hair fit poses (except 2 I made myself), but I assume these are just poses that scale and translate the hair.

This is how I would do it. Apply the hair to the character you want to fit it to. Then scale and/or translate the hair untill it fits the character. Parent the hair to the UNIVERSE, then delete the character. Save the hair to a Props pallet.

Open the pp2 (prop) file you just created in the free utility MAT Pose Edit, use the option to load pose and morph data. Delete any channels that you did not use when fiting the hair to the character. Use "Save As" from the file menu to save a pz2 (pose) file, this will be your "hair fit pose".

Delete the pp2 (prop) you saved, as it is no longer needed.

Getting prop hair to fit should be pretty simple, conforming hair requires that the hair have the same joint centers as the figure, though. That is part of what I change with my hair-fit poses, the rest is as lesbently said.