If rationality is about overcoming bias, then I think of the "dark arts" as the weaponization bias. While we don't believe bias ought to be wielded as a weapon, learning how to swing a sword is vital to defending against it.
In this post I'll discuss a dark art I call "inception". Inception is a 2010 film whose premise is planting an idea in someone else's mind (through the power of dreams). Leonardo DiCaprio's mission to is to plant in Cillian Murphy's mind the idea that he should dissolve his father's company.
Why the idea had to be "planted", and not merely communicated in normal conversation, is because people are very attached to their own ideas. No one wants your ideas, regardless of how much more meritorious they are. People have a very strong attachment to the insights they came up with themselves. No one defends, evangelizes, or holds on to an idea more vigorously than one that they came up with themselves.
This bias the basis of this dark art. The art of Inception is about getting people to come up with your ideas. Obviously, this is counterproductive if you want credit for your ideas, but the upshot is your idea gets the vigorous action in a person that accompanies idea ownership. Inception is more powerful than mere conviction.
I'll now describe the basic method. I'll be putting it into a corporate/organizational context of "incepting" a decision maker with an idea X, but the method is general.
The wrong thing to do is to meet with the DM, present X, and all the reasons why the company/nation/org should accept X. You might accomplish conviction, but you won't accomplish the much-more-powerful inception, and that's what we're going for here.
So instead of directly communicating your full idea like an honest human being, you want to act as a means for the DM to figure out the idea "on his own". It won't really be their own realization; you'll have carefully guided them to realizing your idea for themselves. Here are a few variations on how to do this:
In the 1950s, Betty Crocker devised a cake mix for busy housewives. All you needed to do was mix the dry ingredients with water, put the the pan in the oven and bake. But that proved too "complete" -- housewives felt guilty over how easy it was, and the product was failing as a result. The solution? BC added one step to the recipe: "add an egg". An instance of the "IKEA effect": we value things more when we put effort into them.
Let's apply the same concept to ideas. Instead of presenting our actual idea X, let's craft an "add-an-egg"-version X'. X' should be flawed, but not more than a few steps away from X. Furthermore, these steps should not be too difficult for your DM to identify & correct. The more work put in by the DM to make X' into X, the better & more likely they will come to identify X as their own idea. But over-do it and he might fail to recover X altogether. The Betty Crocker example is instructive; even a single simple change, that transforms your bad idea into "their" great idea, should do the trick.
To your boss, it will feel as though you came with some mediocre idea X', and after a discussion with you, a greater idea X emerged, which he will feel some ownership over.
I should remark that this is harder than it sounds. If X' isn't crafted right, your DM might not think it's worth it to discuss/think about. So it's critical X' has the right balance of genius and error.
This works best when your great idea is the natural answer to a very pressing question. "Natural" meaning, if someone else were to seriously think about the problem, they would arrive at the same answer X as you.
Identify which question/problem Y that X is the answer to. Then when you meet with your DM, meet to discuss Y, not X. You can try to guide the discussion in such a way as to arrive at X, without coming close to actually proposing X -- that would blunder away the whole point of this exercise, which is for your DM to come up with the idea himself.
This is a game of patience and cunning. If you must become more explicit in your cues, always try to externalize them. Send a link to an article or youtube video that you think might spur the idea you're trying to get to. Maybe even contrive some scenario at work that you think will lead to an "aha" moment. You can get creative with this, but beware of coming across as someone who speaks in code.