How do i use hidden skins?

How do I use the skins that are hidden in the mpq without exporting/importing and thus making the file larger?
For example Abilities\Weapons\RangerMissile\HeroRanger.blp

Abilities\Weapons\RangerMissile\HeroRanger.blp

The above is a projectile art.....

As for changing models to a hidden one like the orc wolverine
( Units\Demon\ChaosOrcRange\ChaosOrcRange.mdx )
or the gargoyle spire - building
( Buildings\Undead\GargoyleSpire\GargoyleSpire.mdx )
Just copy the path and go into the object editor and double click
on "Art - Model" and paste the path in the box that already has
a path.

Umm.. i know how to use hidden models
Thats not a model, the path seems like one, but it isnt
Its a skin
Heres another example: Buildings\Orc\WarMill\LumberHut.blp

Ah, There are lots of hidden skins too... but skins are declared in the models, so the only way to use one would be to edit a model...

The best (read: least map size) way to get that skin on a model is to extract it and rename it. The model it was intended for was the Sylvanus Windrunner hero, although it should work on Shandris, the high elf and night elf archers, and probably the Dark Ranger, too.

Here's the renamed skin. Put it in a Units\Creeps\SylvanusWindrunner\ directory.