The fourth and final part of the book discusses immunizing strategies (ways of changing ideas to protect them against criticism to try to avoid refutation). The book says these strategies are costly. I agree.
In general, changing ideas, by adding exceptions, or any other ways, ruins the explanation. So the ideas lose their appeal and the new ones are actually really easy to criticize for lacking a good explanation, even if they're hard to criticize empirically. David Deutsch covers this in his books, especially the dialog about induction which is chapter 7 in The Fabric of Reality.
So I consider this topic already covered and not terribly interesting because it's easy to see the answer from more general principles.
Another way to look at it is that if you can easily vary an idea in the face of criticism, then your idea is easy to vary. You may hope this will protect it against criticism, but being easy to vary is itself an important criticism (as Deutsch explains at length in The Beginning of Infinity). So this kind of thing doesn't work.
I think the problem situation which is concerned that people will try to avoid criticism is wrong. What do you care what they do? People can live badly and there is nothing you can do to stop them, other than violence or persuasion. And if they don't want to be persuaded by you, they won't be, at least not directly. They don't have to listen to you at all, they don't have to read your books or arguments, they can turn off the TV or radio when you come on, etc... People have to use some of their own initiative to learn things. It's a choice.
I think the problem situation which is overly concerned with immunizing strategies, and big general principles like "is human nature rational enough that persuasion will always work?" is too concerned with proof, with formal argument, with having some sort of rules of the game under which progress can be made that people cannot resist. It's concerned that if people have free will they may use it badly. It wants guarantees for reason, progress, etc...
But I don't mind if people can make choices, even bad ones. I'm happy to tolerate diversity. I know that will include irrationality and other mistakes, but so what? I draw the line at violence but that's it. I recognize my philosophy is fallible and conflicts need to be worked out by reason, to the extent people want to, and if they would rather do something else for now that is part of freedom. There are plenty of people interested in learning things who might want to read my writing or have discussions or improve society, and that's good enough. We don't have to make every single person pursue our vision of progress or find some way to prevent them from choosing to ignore us; we shouldn't want that, it's anti-liberty.
Let people do whatever they want, don't worry about it too much. Offer them value and some people will come around because they are motivated by their problems to seek some solutions and they find value in what you have to say. Some of them will tell their friends, persuasion can happen and can spread. We don't have to worry about people shutting out our criticism because reality provides criticism too -- problems are inevitable and motivate people to try to improve. People who don't have bad lives and in the extreme it becomes obvious their lifestyles are worse when they have a thousandth the wealth we do or that kind of thing. People notice that, even bad people, and make get jealous or angry, but the point is they don't completely ignore all their problems and do care to improve, so there's nothing to worry about. I think this sort of perspective is a better problem situation than trying to figure out what to do about people who don't want our help -- the proper answer to that is to leave them alone.
Live your own life, make it awesome, cooperate on a voluntary basis with the best people you can find, offer up value with mass appeal if you want. The book tries to solve a problem that this sort of good attitude to life doesn't have. And the more you start worrying about trying to find ways to stop people living irrationally in your view, the closer you may get to intolerance, tyranny, anti-freedom.