Don't know of a cure time, I usually do them after the weekend wash and unless some strange phenomenon ( known as rain to some ) happens they do not see water until the next wash. When it does rain, sometimes weeks later the rain repel is still there and bug debris also cleans off easier. What problem do you have ?, maybe contaminated glass ?. Is glass clean when doing baggie test ?. Just throwing ideas out there. I also use glass polishing microfibers when using it if that may make a difference.
Dave