Usage patterns
納豆をかき混ぜるto stir natto (to develop its stickiness)
I stir the natto well before eating it.
納豆に〈物〉をかけるto pour/add something (e.g. soy sauce, mustard) onto natto
I eat natto with soy sauce and mustard poured on top.
納豆が糸を引くfor natto to be stringy/sticky
When you stir natto, it becomes stringy.