For me the issue (Harwich problems aside) has been more the poor interchange arrangements and info at the Schiedam end, especially if one is on an international ticket, in particular in light of the paucity / absence of staff (RET or NS) and the need to get through those ghastly barriers. The first time I did it towards Hoek, it was pure chance that I found the (very inconveniently located) bus stop, after having "tailgated" somebody through the barrier.
Why should barriers be a problem with an international ticket? The ticket gets you through the barriers.