Opening the pool has gotten easier over the years. I stick with a formula of draining out the old water, power washing the inside, repainting and waiting for it to dry - 2 days...
You have to treat the pool with the right chemicals. The goal is to avoid algae growth. Always put a full bottle of stablizer and 2 extra blue shock packets. Fill your floater with at least 5 chlorine tablets and if you want, you can add Ph up (alkalinity) to soften the water on the eyes. Shock once a week or after a few heavy rains to treat the fresh water. Keep filling the floater after the chlorine tablets melt down.