A lot of the basics are covered already, so I’ll add what helped me avoid that “why does this feel off?” phase after reopening.
The biggest change I made was not trusting the first set of test results. After months of sitting, the plumbing and shell usually have stale water pockets, and the first heat-up shakes a lot of stuff loose. I fill, clean or swap the filter, bring it all the way up to soaking temp, then let it circulate overnight before doing any serious balancing. pH and alkalinity almost always drift once the jets start aerating again, so adjusting too early just had me chasing numbers twice.
I also pay attention to how the jets feel, not just whether they turn on. Weak flow or uneven pressure usually means there’s still air in the lines or debris sitting somewhere, even if the pump sounds fine. Letting it run a full cycle with all diverters open usually clears that up without me touching chemistry.
Last thing is patience. I don’t soak the same day anymore. I give it 24 hours, recheck sanitizer demand, and see how the water looks the next evening. When I started doing that, the water stayed stable way longer and I stopped fighting cloudiness a few days in. Anyone else notice tubs always behave better on day two than day one after opening?