You'll have to pass the 5 seconds playing time mark. How you do that, either by regular playing of FF doesn't matter.

I do this all the time, but for me this is much easier to do with my Kenwood RC-600 remote because it has separate FF & REV buttons. (the "+" & "-" buttons on the photo - I love this remote!).
I don't think I would bother with the original remote because a long button press (which is needed to FF) takes about 5 seconds to complete anyway so I think I would just let it play then.