I put a f/t pinky in with each new hatchling the day of, or after, their first shed. If they refuse that first meal, I used to offer again in 3 or 4 days, but decided to wait the 7 days that the feeders wait to get their next meal. If they refuse that second f/t offering, then they get offered a brained or sliced pink. If they refuse that, I'll try live. Usually if they've refused live, I'll keep them around long enough to keep offering food if I have extras, but otherwise they get culled off for king/milk food. I don't generally waste too much time trying a bunch of other tricks. If things get slow I may force feed a mouse tail and then offer a f/t pinky again in a week and sometimes that does the trick as well.
D80