On the other hand, some players are really bad handling player vs character knowledge and that can ruin any twist....
Like some player's character is secretly a werewolf and you let the players in on it. Suddenly one of them wants to deck himself in silver weapons even though there weren't any signs for the character to ever encounter a creature where silver would be useful.
While that is true, I'd go further: no one is actually good at handling player vs. character knowledge. The difference in reading a mystery novel where you don't know "who done it" and the experience of reading one where you do, isn't merely in the satisfaction you have when it is revealed or the loss of engagement you have in figuring it out for yourself, but how you experience and note the clues the author provides. Deprived of firm knowledge, the clues in a story can pass you by as extraneous information, or naked facts which can't be connected to the larger narrative. But if you actually know who done it, everything you read will be checked against what you know about that character, and conversely every detail of that character will be received as a possible clue. In short, you are much more likely to realize the significance of everything you read than if you didn't have that context.
So metagaming is rarely as overt as you describe. The more usual effect that it has on a game is that the character acquires the player's knowledge, curiosity, suspicions and reasoning as soon as any clue is revealed. With firm knowledge regarding "the truth", the player's guidance for the character becomes a laser like focus whenever any in game knowledge is presented to the character. And the important thing to understand is,
this sort of metagaming is entirely and completely unavoidable. It's certainly possible that the character/player could have had their curiosity aroused and begun a persistent investigation of something and figure out "the truth" or at least begin to strongly suspect it on the basis of a single clue. The player is placed in the position not merely of having to ignore what he knows, which is fairly easy, but to deliberately act stupidly and ignorantly in situations where the character also might reasonably know or suspect. The player could of course
choose to act stupidly and ignorantly in the face of in game information, but if he does so he now is metagaming. So the player is placed in position which is not chosing whether to metagame or not, but rather chosing to metagame to his advantage or chosing to metagame to his disadvantage.
For the vast majority of traditional role-playing games, which require the player to advocate for his character, most reasons why you would choose to metagame to own's own disadvantage is not playing the game correctly. This is particularly true in cases where it would be playing the character against his personality or abilities to not be persistant, curious, insightful, rigorous and so forth.
Fundamentally, there is no way to pretend to be ignorant that accurately reflects how you'd behave when you actually were ignorant.