A dishwasher rinse aid to prevent water spotting?

My well water goes through a whole house water softener, but apparently "dissolved solids" pass through. I once tried a few ounces of distilled vinegar in a gallon or so of water from my dehumidifier* as a final wipedown with some effect, but wonder if it deteriorates a wax finish or otherwise affects trim parts, etc.
Glassware comes out spotless from my dishwasher, so I've contemplated trying a bit of Finish. I think it wouldn't have adverse effects on the car, other than removing some wax, etc. Has anyone here tried this method with success?
Also, I don't wan't to use a hose inline filter, as they need a fairly expensive regular replacement, and perhaps don't remove dissolved solids anyway.

* Essentially distilled water, and I check and clean its filter regularly.