I learned a lot from porting ICE9, and a lot of it involved me relearning some of the things I thought I had mastered. I would prefer to write a guide after I port another theme so that the foundation is solid.
For now, I recommend those who would like to learn to this page:
It has a lot of information which I have been learning from. I don't use the same tools as he does (in fact, I don't think anyone uses the same tools...), but it's a good start.
Some of the tools I'd recommend (though their use will remain unanswered) are: WinMerge, apktool, RegexRenamer, and FrameworkFlasher. I hope to mention these in the future guide