[sanderjd]

I think the hard part mentally (that your incredibly great explanation completely alleviated) is trying to guess at the meaning of the interplay of all the instructions, addressing modes, register overlaps, and calling conventions. It seems like the only way to turn that from difficult (impossible) guess-work to mere sand-unloading drudgery is to either have a lot of it memorized already, or to have a very strong command over the various documentation resources.