For next time how do you think I can write my private key in code safely but easy enough to decode by hand?
I wouldn't try to encode/decode by hand. I'd generate a random 256 bit number, perform an XOR between the random 256 bit number and the bitcoin address, then encode both the random number and the result of the XOR in something like base58. Next I'd have two different engravers engrave two separate items, each engraving one of the two encoded strings.
To redeem, you'd perform a bitwise XOR between the values represented on the two engraved items, and import the result as a private key.
In reality, this is all more effort and risk than I'd prefer. I wouldn't use an engraver at all, and would find some other method of long term storage that doesn't require me to reveal my address or encoded private key to another person. If you've got your mind set on involving untrusted people to assist, then I'd want to introduce a significant amount of unpredictable modification to the value that you are sharing.
