What GP means is to go to a grocery store and lay out 10 American Dollars for an Apple-branded services gift card (what used to be called an iTunes Gift Card). One of these: https://www.apple.com/shop/gift-cards
You apply it to the brand new Apple ID you've made and use those virtual funds to make the in-app purchase in the Twitter app that, at the time, was the method of paying for Twitter Blue. (The purchase page even said/says, "You can only subscribe on the Twitter iOS app (for now).")
No blocking of prepaid or gift cards here; you're doing exactly what Apple wants and it's not Apple's problem that Twitter takes IAPs for a "verified" service.
I'd be too worried about getting charged with wire fraud or something personally.
It's normally combined with recorded IM conversations along the lines of "bro, I bought some short term chickens for Lli Eily. Let's make them CLUCK with this tweet." You call them chickens, or something similar, to try and fool the FTC. This is also a surprisingly common occurrence during insider trading investigations.
1. Create a new Apple account
2. Buy a $10 iTunes gift card
3. Use that to pay for Twitter Blue
Would I pay $10 and twenty minutes of my time to knock $20bn off of an insulin profiteer's stock price? Absolutely. Put me down for a recurring subscription.