I have almost the exact same process. Instead of under a lamp I run it under warm water (in a bag) For a few minutes.
When I present the rat I scratch at the substrate with my tongs until the snakes poke their head out then offer it just far enough away that they have to come out of the hide. I usually offer it tail first because it is softer and my snakes strike hard. Plus it is easier to grip rats with tongs by the skull. I shake it then hold it still then wiggle it then still until they strike. My little one will come out and tag a rat within 2 seconds it seems but the oldest ones and my sand boa need some more coaxing. All my snakes have "only accepted live" but I've had zero trouble feeding f/t. The first time I try i also wait an extra two or three days too and it has yet to fail me
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