Why wait for it to evaporate when you can just remove may be 2 gallons and then start the drip method right away with the higher salinity?
Why you ask :::
it would be the safest way to do it as he is still in the learning stages of the hobby.
and we rather see him comfortable doing something he is not 100% sure about . it also simplify s the chemistry
and it makes it so it is impossible to raise salt value to fast putting the livestock at risk