Swift uses irony when he says the person with whom he discussed his plan is very worthy and a true lover of this country
The used rhetorical device is Hyperbole.
Saying that something is a billion times better is hyperbole because it is not really that much better, you would just be over exaggerating.
This is only 15 points what a lie but ok.
British gas
a little penguin goes to a planet and fixes boiler
to show British gas it good and best for the people
persuades using them as a cute penguin
cartoon
very effective
An advantage would be that it would be first hand knowledge, so you could find out how normal people felt about situations.
A disadvantage would be that they are likely to be biased.