If there would be a legit and sure way to get big airdrops, everyone would be using it and after a while that technique would be rendered ineffective as value is based on scarcity and you can't just gift everyone something and expect it to have value.

I have minted NFTs and traded them that has given me ton of money via airdrops later on. But that doesn't mean Minting NFTs is the key. I was just lucky with my timing. Same thing goes with everything. Be one of the first one doing something that no one seems to yet understand or be interested in, and if that is going to be next big thing, then you have hit gold. But it's all luck. There's no one way you could say it would work next time.