I've had pretty good success starting hatchies on f/t. lol Once I figured out what I was doing
Here is exactly what I do:
Wait a week after the first shed (unless there's a hatchling with an issue, it gets special treatment). 7-8 days after the first shed, I thaw the needed number of hopper mice at room temp for a few hours in a corning wear dish.
After dark, the whole dish of tiny mice goes under an incandescent light bulb until the bottom up the dish is warm (not hot!) to the touch. It takes a little under five minutes. Temp gunning usually shows the mice and/or dish at ~120 degrees F. They very rapidly cool.
When starting with f/t, I never zombie dance. Ever. Each of my babies gets a hidebox and I set the warmed hopper in front of the entrance as smoothly and quietly as possible, going down the lines of little tubs.
Then I leave them in darkness overnight and record who ate and who didn't. Usually 7 days later, I repeat. Babies that don't recognize it as food twice in a row get switched from PTs to aspen or cypress (whichever I have on hand). Two more refusals and they get live crawlers. Then it's two or three live feeds and I go right back to f/t. Knock on wood, it's worked so far. It seems like most of the time, the problem is whether or not they feel secure. My most nervous hatchlings are always the last to start.