One part of HPMOR that seems especially relevant here is the "spend 5 minutes actually thinking about the problem" technique.

If you're facing a big, important problem, it's natural to suppose that solving it would take a whole lot of time, work, and skill. Maybe so much that it's beyond your capabilities, in which case you can write the problem off as impossible. But presumably at least enough so that it makes sense to put off thinking about the problem until sometime when you have a big chunk of free time to focus on it, and are feeling especially cognitively sharp and motivated. Right?

Turns out that if you spend 5 actual minutes thinking about the problem, that is sometimes enough to solve it (or at least make substantial progress). Especially if you are the Weasley twins, and the problem is a spectacular prank.