The quick answer
Remove large debris, restore normal water level and flow, brush settled material and monitor the filter before adjusting chemistry.
Start with surface and baskets
Skim leaves and large debris before they sink. Empty skimmer and pump baskets so circulation can work normally.
Brush fine material
Dust settles on steps, benches and the floor. Brush manageable amounts toward circulation areas without overwhelming the filter.
Monitor pressure
Fine debris can load a filter quickly. Compare pressure with the clean baseline and follow the correct procedure.
Test after mixing
Storm debris increases sanitizer demand, while rain can shift water levels. Circulate, then test.
Look beyond chemistry
Weak flow, a noisy pump or returning debris can signal equipment trouble. More chlorine does not remove dirt.