If he's already impressed with you, just ask him for something. Whatever it is you're hoping to get out of this. If he is indeed an INTP he's not gonna just give you something because he likes you, but if he likes you he'll give you something because you ask. Just continue to be impressive and then plant the seeds of "if you ever need something like this again..." or "you know, I can also..." or whatever it is you want.
Then again I've never really held down an honest job so take this for what its worth.