Hi, Mariana! Great question.
Personally, I don't think there is one correct tool for this task, and I don't think you need any fancy crafting tool either. I usually just use a paring knife to gradually angle the edge, or a microplaner (fine hand grater) to fine-tune the joint or if I don't need to shave off a lot. I know some people use electric wood mitering tools for this task, but I've never had the need to invest in one. I also prefer to use kitchen tools on food items. (Though to note, most of my constructions are fairly small. So perhaps an electric mitering tool would come in handy on really large-scale constructions. I'll be interested to hear how others answer this question.)
Anyway, here's a slide from a presentation I'm giving this weekend that shows how I gradually pare down the edge with a paring knife - I hold the knife much like I would if I were peeling an apple.
