This is after the 1.04 Patch and is working as of 11/10/18

Start up the map with a starter pistol
Shoot all your ammo out
kill zombies with knife to fill specialist bar
pull out the specialist then get killed while you have it out (or hold grenade)
have a teammate revive you
fill up specialist meter by knifing zombies
pull out specialist and it should be unlimited

Happy glitching Awesome face