I was able to get my Togepi from imported SS to, like, 8 levels, and I only transferred it back and forth a couple times, if memory serves.
Remember, it is MUCH harder to understand how the thing works when it's in Japanese and you don't know ANY of the language.
/still wanna try and see if I can use the Japanese PokeWalker with the American HG or the American PokeWalker with the Japanese SS and vice versa