I got a new liner in the fall and got the water cleaned up, pH adjusted, algaecide 60 in and closed it up and put the mesh safety cover on.
So now it's a month from opening and it's apparent that I don't have any CYA in the pool due to the new water. I added chlorine and it was gone in a week.
My thought is to dissolve enough CYA powder in 5 gal buckets to get 20 ppm CYA and pour it through the safety cover. Then I could add chlorine/maintain chlorine until I open the pool.