2nd the hairdryer method. Basically, thaw the rat however you usually do in the same room as the snakes (scent the air), then pop the cage open and nearby spend 30-60 seconds blasting the face of the rat with hot air. I wait till I see a nose and tongue working from a hide and offer. If no strike within 15 seconds, repeat the heating as it cools off fast.

I got a stubborn ex-breeder adult male (guessing 3-5 years old) who was on a winter fast and supposedly "ate either frozen or live" and proved to be a live-only snake... using a hair dryer and not giving in for a few weeks of missed meals did get him to switch. Initially, I skipped a meal while he was blue before a shed, and by the 3rd weekly offer after he shed out, he accepted the frozen rat. The next offering was then taken with as much gusto as he had on live rats, and he has eaten frozen ever since.

Sent from my SM-G950U using Tapatalk