To be honest I wouldn't go down the rabbit hole of scenting mice. Your Stimmie has a history of eating, no point making things overly complicated.
Simply defrost your mice in warm water as suggested above (do not microwave or boil). Feel the abdomen of the mouse to ensure there are no "cold" bits left - in fact you want the mouse to feel warm to the touch.
Once satisfied simply offer with tweezers - You may or may not need to shake it slightly. Some fussy eaters can be tempted to eat by "braining" the mouse. You may not need to, but if you do it simply involves pushing a knife or razor into the head of the mouse to get some brain matter exposed. You are not paying for scenting and it is extremely quick to do, if a little messy on occasion. Something about the smell can get some snakes going.
Still, if it doesn't eat for you on the first shot just give it a week and try again later. S/he'll be fine.