If I were to find a dead Canadian, who is deceased long enough that all copyrights they hold have expired, and if this person has no heirs, and if this person has no departing legal requests regarding their legal property (eg: a will), could I transfer my copyright to them, and in doing so end up with my work immediately in public domain with no way for anyone else to claim copyright of it?
It doesn't work, just like transferring the copyright to a young person to make it last longer doesn't work.
In places where the length of copyright depends on the death of someone, it always depends on the death of the author. You can transfer copyright, but you can't change who is the author. If I write a book, and some copyright law says the copyright ends 70 years after the death of the author, then it ends 70 years after my death. It doesn't matter who owns the copyright.
PS. That dead person has heirs. If there are no relatives alive, then the government of their country will inherit everything (in most countries, there might be exceptions). Your plan fails for that reason as well.
PS. See "Just a guy's" answer for another, completely different, reason why this scheme doesn't work.
No. The dead are generally not considered legal persons. They have no rights, and cannot own property, make contracts, sue, and so on. Giving them copyright would make as much sense (legally) as giving your rights to Niagara Falls.
(Even if you could give copyright to a dead poet, it wouldn't help. As gnasher points out, copyright usually runs for 70 years after the death of the author. So even if you could give copyright to the dead poet, you'd be giving copyright to her heirs.)
Since only the author or creator can claim copyright, you don't need to worry about others getting copyright in your work. You can declare that your work is in the public domain. In most countries, this act is enough, and it is irrevocable. Or you might look into using a Creative Commons License.
No need to bother.
Just declare the work to be in the public domain. Doing so entirely destroys the ability of another person to claim copy rights on it.
But public domain doesn't protect you much.
So it's in the public domain. And someone else grabs big chunks of your work, adapts, remixes, and publishes it, and copyrights it, the audacity! They can do that. It's in the public domain.
Or to be more precise, you can't do anything about it. They might of course be subject to plagiarism, moral rights, and other stuff... but that would be a relevant authority versus them - you have no say in the matter, except the defense will force you to testify that you did place it in the public domain.
It will have a different effect on patents. Nobody will be able to patent any idea in your published work, because your work will count as prior art. But the work doesn't need to be in the public domain to have that effect.
You can also emplace some sort of alternate copyright scheme, such as CopyLeft or GPL. In fact, you already did that just here and now, by submitting the question.