how long it would take depends on the snake. I'd start by not feeding for a week or two so he's nice an hungry. Let you f/t mouse defrost on your counter or where ever, just don't ever microwave a frozen rodent. I like to warm up a mug of hot water in the microwave and then put the mouse in a bag and leave in hot water for 20 mins or so. after its thawed and has been warmed up by the water offer it to your snake. you might try moving it around to mimic a live mouse. if he takes it move it around to simulate a struggle when he coils up on it. If this doesnt work you might try fresh killed, it's a little more violent but it might be needed to segway to frozen thawed?