Magic is essentially like any other ability in MU, some people are born with a preposition to it, but it can be mastered with hard work. Also, this could be of use (http://en.wikipedia.org/wiki/Category:Fictional_characters_in_Marvel_Comics_who_use_magic). In Doctor Strange's wiki there's a bit talking about the specific rules and regulations, and lack thereof that might help as well.

ALSO THAT FIC. I actually lol'd at the bit about Jan ~tweaking~ his otherworldly clothes. That was very touching, thank you for sharing.