I am new to alternas myself, having gotten my trio of 08s last year already feeding on mice. I know from reading these posts, and talking to others, that some have to be started on lizards, or at least lizard scented pinky mice. Others lines seem to be easier to start on mice. Some breeders brumate their hatchlings and find it is easier to get them feeding the following spring.
With my cornsnake hatchlings, I waited until after they shed, and then most fed right away on pinky mice, live or F/T (except this one, who couldn't wait!)

I am hoping to have baby alternas in the next year or two, so I will be figuring it out too.
Maybe some that are more experienced will have better answers for you. You might also post this question on the king snake forum.

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Kent
0.1 Hypomelanistic striped cornsnake
0.0.3 Hypo (het lavender, striped) cornsnake hatchlings
0.0.5 Normal (het hypo, lavender, striped) cornsnake hatchlings
1.2 Gray-banded kingsnakes, blairs phase
1.1 Oregon rubber boas