I’m not sure that there is any one “right” technique with picky eaters. Both of my kids were relatively picky as toddlers. One outgrew it and is now an adventurous cook and eater. The other (with Aspergers) is still extremely picky, but making slow progress. And I used the same techniques with both - present wholesome, varied meals and snacks and let them take the lead. The only time we ever cajoled was to make sure that S ate a protein every day (allergic to peanuts and didn’t like meat). Occasionally we had to bribe with extra video game time to get him to eat an egg or a piece of cheese. (Ha! as I’m writing this he has just requested a pulled pork sandwich - on white bread, with no sauce and “make sure there’s no fat on it” I told him to make it himself.)