I do exactly the same - not with 4-way stops as we don't have those in Germany, but with areas where a two-lane road is intentionally narrowed to one lane for a very short piece of road, which we sometimes have in order to slow down traffic around pedestrian crossings. If I see someone approaching from the other side and we are about to arrive roughly at the same time, I slow down just enough so the other person hopefully realizes she can go first. If I see the other person doing the same I add light flashing, which is typically understood as "You go first". But it is rarely necessary, because if I start going slow early enough, the other person realizes he/she is a tiny bit closer to the narrow part, so they slightly speed up in order to ensure they are first and thus get the right to come through before me, which is exactly the reaction that I want, because my interest usually isn't to get through first, but to be able to roll through the narrow part without coming to a full stop.

When I was road tripping in the US, I also attempted to prevent unclear situations at 4-way stops by intentionally slowing down just a bit so it is clear that I'm not first to drive. Since I couldn't prevent the stop anyway I was usually much more comfortable with letting other people drive first, or at least with having a clear order and knowing about my position in that order.