Many of these methods involve lying, or at the very least misleading.
Not that narcissists don't deserve this kind of behaviour in response, but I just don't want anybody to be encouraged to sin, no matter the insanity of their adversary.
Myself, I think I may have developed some kind of narcissism down the years. As much as I try to convince myself otherwise, I've always had the feeling that I'm far more intelligent than I am. Obviously, as I'm sure plenty of those who've argued against me on here would know, this is ridiculous. But it's a feeling I find difficult to shrug off nevertheless.
Beyond that: I never used to be vain, I promise, but rather it was actually a convincing that I was ugly that led to me becoming obsessive with my appearance. I usen't to ever think about my appearance at all, from my youngest years to my mid-teens. But once I became convinced that I looked, well, unfortunate(to say the least), and that this impacted my life severely, I began to obsess over my looks quite a bit.
Nowadays, I'd consider myself quite a self-obsessed person altogether, which is quite an awful thing, and is also something I don't think I ever would've expected myself to become as a boy, but here I am. I don't know how well these methods work against me, but insofar as they're licit, I encourage anyone to try.
Anyway, I doubt narcissists have the best ideas as to how to deal with narcissists, but I thought I'd give my 2c.