I definitely use the sandwich to offer criticism. Usually, it ends up with child defensive and voice rising to almost a scream at me and then me telling child, oh no you don't....

Discussing different scenarios of how something could have been handled differently and then asking if maybe, now that you think about it, is there was a better way to deal with the situation other than (insert over the top reaction) that occurred will hopefully pan out for me. It's far better received to turn the tables and make them empathize than to say you were wrong for doing X.