There are services like Airhelp [1] which do the legal part for you, for a small cut. I've used them several times when flights were delayed.
You can pay a company to do it for you, and onboarding with them takes longer than a half hour.
I would use them only after trying to do it yourself.
My daughter was trying to come home from university this summer and they canceled her flight twice while she was in line at security. Guess what Wizzair said.
She has claims opened with Airhelp now, we'll see what happens.
A quick e-mail to the airline with the order number, stating the expected flight plan, and comparing it with the actual flight plan and a calculated delay have always worked, even with the cheaper airlines.