[his reputation of "that hero that sometimes does magic on the streets" of course!! . . . which was still a small reputation, but he was doing his best to build it up. all in due time]

You just sorta. . . [he trails off, trying to think about how to put it into words] Find a spacious area and attempt to cast the spell a few times. You sorta figure out things like technique, limitations, and such as you go.

[in other words: trial and error]