My interpretation of the explanations in the 日本語表現文型辞典 is slightly different. This answer could be incomplete and missing important details, so I hope someone else can write a more comprehensive answer, but based on the information available to me right now:
For 〜といい〜といい in the 日本語表現文型辞典:
"It's used when the speaker wants to say 'however you look at it, it's ...' in regards to a certain matter/thing, presenting a few examples when the speaker wants to give an evaluation/opinion."
And it puts it under the primary heading "〜も〜も".
The 日本語文型辞典 says it's used to present two nouns as examples, and it frequently (though I don't think always) carries the nuance of that it's not just those two, but others as well. It says a similar thing to the 日本語表現文型辞典 in that it's used in sentences of criticism or evaluation with special feelings (like being amazed, admiration, resignation etc).
From this, I'd translate the above as:
Both exercise and study, no matter what I do I'm hopeless.
The progressive dictionary also has a definition for 〜と言い, and defines it as "both...and...", or "neither...nor..." in a negative sentence.
For 〜といわず〜といわず in the 日本語表現文型辞典:
"Giving a few examples, you use it when you want to emphasize 'without discrimination to ... or ..., everywhere (every time, every one, everybody, etc)'"
And it puts it under the primary heading "〜も〜も区別なく".
The 日本語文型辞典 says something very similar, saying it repeats nouns which represent a part/section of something (so I presume the nouns represent a smaller subsection of a larger category), and expresses "without discriminating, all".
I think to represent this, you can append an appropriate "every*" word to the sentence, the progressive dictionary has an example of this.
From this, I'd translate the above examples as:
Talking of the Japanese, no matter whether they be adults or children - everyone - reads Manga often.
It doesn't matter whether on the hands or feet - everywhere - the child returned home completely covered in mud.