Everybody probably knows about this. But whatever.

I play on the Xbox, so I'm not sure if this is cosole specific or what... Anyways, simply go in to sneak mode with your weapon sheathed. Toggle to third person and draw your weapon as you walk forward while still in sneak. After your weapon's drawn, you should be sneaking super fast (about as fast as you'd run out of sneak) as long as you stay in third person. There you go. Hope that helped or whatever.