Firing the 3rd barrel

[Spicymoose]

What types of hands and boards should we be firing a third bet on the river as a bluff?

I would imagine it has to be a hand where you are in position, HU, and have a hand that virtually cannot win if you check.

For example, if you open raise and AKo from MP and only the BB calls.
Flop comes 2d7h8d, he checks, you bet, he calls.
Turn is Qc, he checks, you bet, he calls.
I would check almost all rivers UI.

If, on the other hand, you had JdTd, maybe you should bet a blank river when he checks to you?

Can anyone give a clear hand of when it is right to bet the flop, turn, and river with a hand worse than 1 pair?

Obviously I would like to know when this is ok vs an unknown, but what type of player would make you even more inclined towards doing this?