You probably read this article here:
Which essentially argues that based on past depositions, Trump is a better liar under oath because he is more careful in his answers. He'll say he doesn't remember things he probably remembers, which is the kind of lie that is easy to get away with.
This seems at odds with Woodward's description of when they tried to prep Trump for the Mueller interview, where he essentially just lied recklessly like he does in public. Maybe Trump smartens up when he actually starts the interview. Or maybe Trump is less disciplined now because he's losing it over the stress of a job he can't handle and specifically over this Russia probe. I'd like to put it to the test.
Best way to get Trump to disregard the advice of his lawyers is to bait him. A good op-ed in the "failing New York Times" which, if you've read further, you know that Trump privately believes is credible, would do the trick. Say that Trump can't handle Mueller and would be eaten alive, that Trump knows this and that's why he won't do it.