When I do a split-S or make a sharp turn around an object, my drone shakes due to the prop wash. I have heard that this prop wash (from abrupt turns) is the hardest to remove via tuning. I've tried messing with the PIDs, and the filters. I'm running RPM filtering, so I started with filters in the middle (default) of the sliders, and gradually moved them all the way to the right (least filtering). My motors do not get hot. The prop wash is mostly gone, but I still feel it/see it through goggles, and hear it. Am I wasting my time trying to remove this last bit of prop wash?
I think prop wash is not entirely eliminable by tuning. If you have really good gear and tune you may be able to reduce it even further, but it will be there.
When you are doing sharp turns, you are flying into your own turbulent air stream and the effectivity of your motors compared to each other changes unpredictably and rapidly. The flight controller tries to compensate, but neither the calculation nor the the motors' reaction is instantaneous, so most probably the compensation will come too late and will not achieve the required effect, which will trigger further and further micro adjustments until the quad reaches more predictable air.
So the easiest way to eliminate prop wash is to move out of your own turbulent air as quickly as possible. When doing split-S don't just descend vertically, but start moving forward before arresting your fall so your motors will be over clean air.