What are some techniques for selling an idea for a game prototype and a proof of concept? Along with the advantages and disadvantages of each technique.

There are none. Unimplemented ideas are cheap, not something bought and sold.

SpartanXInfinity347 said:
What are some techniques for selling an idea for a game prototype and a proof of concept?

https://sloperama.com/advice/lesson21.html​

Development deal contracts (or licensing deal contracts, if that's what you're thinking) are not Game Design topics. Moving this thread to the Business and Law forum, where it belongs. Here, you can check out other threads discussing this same topic.

This sounds like a school assignment based on the way it's phrased…

But there are none, an idea is worth nothing, the execution is where it is viable. .

GeneralJist said:
This sounds like a school assignment based on the way it's phrased…

Yup. Locked.