The methodology is described here: https://cyberlaw.stanford.edu/blog/2011/09/tracking-trackers...
Even the DNT header, which is widely recognized as a failure since it relies on the perpetrators to regulate themselves, protects you better against tracking than blocking third-party cookies. It's just too easy to track people by other means, and the companies that aren't already doing it will certainly start if a meaningful number of people suddenly block third-party cookies.
The only pragmatic and effective way to avoid being tracked today is to use something like uBlock (more efficient ABP + noscript) with the third-party script and frame blocking features enabled (whitelisting third-party scripts/frames only on those sites that break something you want to see at the cost of possibly being tracked by something the block lists don't catch.)