First back up the files that you replace.

Go to GTA V/x64v.rpf/models/cdimages/streamedpedprops.rpf/player_one_p
or /player_two_p
or /player_zero_p
and replace the files using OpenIV
it has some bugs if you use long hair it will go through the hat.

V2: added new cowboy hat
(fits perfect on franklin, samll bug on trevor,bigger bug on michael)

To add textures for Franklin Go to:
GTA V/update/x64/dlcpacks/mppatchesng/dlc.rpf/x64/models/cdimages/mppatches_p.rpf/player_one_p
.