Next is to build a signer or address generator to do it automatically ala seedsigner or crux/maix, but in the meantime I made a spreadsheet to help translate the private key into public keys/npub/addresses—you can use any tool to do this and of course #offline is best

Converting 256 bits into digital form is easier than you expect—took about two or three minutes.  You quadruple check, to be sure, as you would for anything of value, and of course you have backups