I'm able to learn Stealth on NPCs such as Ozursus just spamming STOP STALK;STALK OZ over and over. Can lock Stealth with 625 ranks.

You observe Magical Feat Trainer Ozursus's motions, trying to discern the strength of his senses.
As you consider hiding around the Trainer Ozursus, it's around even odds.
You are somewhat uncertain of the accuracy of your judgement.
As you consider an attempt to stalk the Trainer Ozursus, it's around even odds.
You are somewhat uncertain of the accuracy of your judgement.
Roundtime: 2 sec.

This also works on critters, like musk hogs.

I had reported earlier (not sure if it was fixed or not) that the slip STALK verb was teaching at any rank as well, but it doesn't seem to be doing so anymore.

GENT