How do you avoid dealing with the same question multiple times as they work at their own pace?

Students are grouped.  Once I answer a question within a group in a work book, that student is then responsible for teaching the partner or group if the issue arises.  Sometimes if it is a wide spread epidemic then we will do an impromptu lesson on the board.  Nothing really says you can't still do a mini-lesson and does happen once or twice a week.  Especially if the lesson has created a misconception inadvertently, then it is a necessity to address it as a class.  Really depends on class size and you the teacher.