Thisbe never gets the chance to mentor; Manannan always steps in for her. In her moments of lucidity though, she stares at them and whispers a prayer before her mind or the drugs take her over again.
Honorius takes the volunteers aside every year and makes sure they know what they're signing up for. No one knows exactly what he says to them, in a room alone, but they know he gives them a chance to back out. They never do.
Evelyn never gets another one back. She has Nolan, and Ben, and Abram, but in her mind they're Wheaton's, they're all Wheaton's. She can never quite swallow the resentment she feels that her uncaring mentor had four children return, and she has none.
Virtus prefers the Institute to the Control Center. Seeing the unprepared eyes of the tributes, especially the girls, sends him into fits; he doesn't tell his cousins. They already know.
Cora doesn't immediately have tea with Mags and Bovina after her tributes die. She goes on a walk throughout the Capitol, presumably to clear her head and admire the beauty. She's really noting how to tear down each building brick by brick.
Emrys knows he needs to take care of Matthias, knows that no one else will, but goddammit, Jason was the best tribute to come out of Five in ten years, and the Gamemakers just opened up a hole beneath him. He didn't tell Emrys that someone at home might affect his chances; but that doesn't matter, because he'll never tell Emrys anything again. The mentor packs up his station and goes to get some morphling. He can deal with Matthias later.
Justus never mentors. There are more than enough instructors at the Institute, and more than enough District 2 Victors to take the responsibility, so why should he? Secretly, though, he picks one of the tributes as his favorite, talks to prominent District 2 citizens about them, and often nets more money than the tribute's assigned mentor. The Odair method is quite effective.
Chevy uses the Sixatrons. There are always quite a few, and while they don't have the money or the sway of the big betters, they have enough enthusiasm to make up for it. The heavy betters know that Six usually doesn't stand a chance, but having the fanbase saved his life once; why can't it save his tributes' lives too?
Ben is the best mentor District 9 ever had. He isn't that great with the kids, he is hopeless at being friendly, but he can walk into a room and convince everyone, without a doubt, that District 9 is going to make it back next year. All the sponsors have to do is look at him, this man with a wolf pelt around his shoulders like he's just stepped out of the arena yesterday, and their money goes in his pockets. He wishes the image and reality could be the same.
Luster employs the same strategy as Boudicca. His tributes are about as ready as they can be, and if they can't make it out of the arena on their own merit, why would Luster want them?