I have some RED-clips with some extreme hightlights. The soft clip or luma gain will not take them, so the only possibility I see is to change the brightness and flut in the raw settings.
I dont want to change the raw settings as it will affect the entire picture.
Soft clip in R9 is actually not as robust as it was in 8 as far as I can tell. Either way for blown out highlights I usually create a separate node and key in just the luminance of the blown portions and a little just below. Then I raise the mids and blacks and lower the highlights while giving it a hue that matches the image or looks good (usually balanced to white or warm). Raising the mids and blacks near the highlights seems to "soften the blow" and lowering them makes them less distracting. Just my taste though, your mileage may vary.