I'd do a water test to see what your chemistry looks like.

If everything seems okay, which if you have a pool guy it hopefully will be, and if you don't have a vac or anything like that, I'd just get in there and brush all of the surfaces down with the filter running 24/7.

Add enough chlorine to shock.

Brush again, all while keeping the chlorine at shock level. Brush again the next day as needed, all while maintaining shock levels for chlorine.

Organics in the water will consume the chlorine, so initially your chlorine levels may drop significantly over night, say from 20ppm to 15ppm. When you shock at night and the chlorine level only drops about 1ppm over the course of the night, that'll be a pretty good indication that all of the organics have been killed off.

At that point you can let the chlorine level decline into normal range and maintain that.

Then you can reset your filtration from 24/7 to whatever your normal schedule will be.