I think it is ok to do it as the book stated. I have tried it with some small gaps. But you have to use 水砂紙 to 磨滑. Usually, you have to use it with a lower number first, say 400 or 600 (don't use 200 as it is too rough), before you change to 1000. But if the gap was too big and you used this method to fill the gap, it might not work that good unless you wanted to paint it afterward.