You want to add a completely new texture? you need to edit .ymt aswell

@Reacon "combines eyebrows/eyelashes/facial feature textures and makeup into 1 texture file" you can do this with paint.net, find the eyebrow texture you want, find the beard/moustache texture you want and put it on another layer, done
for example i did this

@Reclusive-Eagle ah, but with for example paint.net you can easily add the moustache or anything to normal face texture

x64v/models/cdimages/ped_mp_overlay_txds.rpf here you will find all GTA Online textures (like Eyebags, makeups, facial hair etc)

You can't change that, it will look normal ingame but not in editing tools

Don't use shittdux
Problem solved

@womb_raider For me mp vehicles in sp works

go to slots.xml and there you can add new slots (maximum 7 , 8 in total because there's also "0" slot) then you have to edit pickups.xml to make the weapons show up in these slots