It's a lot harder than it looks. You can 'get' the concept, but to accomplish your goal, it requires taking some wood off, looking, turning, taking more off, looking, waiting, stepping away from the rasp, getting out of the shop, coming back to look, asking someone else to look at it, cutting some more, etc.
Unless you're Mike Brooks, this stuff takes a long time. Don't be fooled into thinking it's easy, but it sure is fun.
Tom