First: find influencers that have an audience fitting of the target audience of your product. Second: yes, you need to pay them. You don't want your company to be known for wanting influencers to promote your product for free.
Yes, but you need to carefully research the audience of influencers. If influencers have the same audience as the target audience of your product. It will work like a charm. As per neuroscience research, the human brain always listens and agrees to recommendations from a person who is very popular and other people are listing to them.
That's how our advertisement agency works. A popular actor recommends you some product and people listen to them.
But Paying is not enough. You need to convenience them about your product. It should be beneficial for the audience and then only they will promote you. (Ideal scenario)
All the best!