Shikamaru's reputation precedes him for good reason. But on this one, I think Kakashi is going to be more useful. He's touted as "smart like Shikamaru, taijutsu like Rock, smell like Kiba, and stronger sharingan than Sasuke", and in addition to all of that, he knows FAR more about Jiraiya than Shikamaru.
Give Shikamaru time and he'll be right there with Kakashi in THIS regard. But as it stands, Kakashi is probably the best source for decoding this one.
Prime example: Jiraiya told Kakashi, personally, that Tsunade's bustline measures 106 CM. Not to mention that everyone knows Kakashi's favorite author.