It seems to me the most difficult rule to follow would be the third - limiting methods to only receive four parameters.
The other rules, while also challenging, seem manageable if your code is exceptionally well-factored. However, I can certainly imagine scenarios where I've needed to pass more than four parameters. It seems this suspicion is well-founded as the example cited in the blog post also skipped over this without a real suggestion for how to tackle it.
This is definitely the only rule of the three that I feel I would have trouble implementing.