I have an easel densitometer that I use, with proper calibration, to set the exposure for each negative. I can set it to read Zones instead of density. I designed and built it myself, so don't ask where you can buy one. Along with this contraption, I have an adjustable light source that is wired to be on (by switch) when the enlarger lamp is on. I use this light for "while flashing" by setting the enlarger for highlights with the flasher off and adjusting the flasher for shadows with both lights on. The object is to add just enough light to the enlarger's that the lightest part of the image is at the paper's shadow threshold. Highlights are NOT affected by any visible amount.

The result is as if the film had had a long toe with upsweeping curve.

I don't use this setup very much because I use mostly VC paper.