For the top whites, I don’t go below the 100% mark when adding any modification. I will take the top white and go down to 50% for a quick comparison but that’s it.
The darker the color (any color), the less translucent it becomes so you can increase the opacity but I usually never go above 50% solidity for greys.
This is just how I do it. If you didn’t use solidity at all, that just means to shift/adjust your seps in a different way. You’d separate “differently.
I know a few great separators (Jeremy Duncan, Bruce Kittle) to name a couple that don’t use solidity at all. All channels are set to 100%. This is how we did it when photoshop first came out. There was no solidity. It’s a preference now, so don’t get hung up on the idea of the right amount.