While in bloom, try to raise the air moisture level with a humidifier or humidity trays. They prefer a slightly acid pH, but most acid fertilizers are too high in nitrogen, producing more foliage than flowers. If the camellia is growing in a peat-based potting soil and you are using distilled or rain water, the pH will probably stay slightly acid. If the pH tests 7.0 or higher, you can acidify the soil by watering with a solution of 2 tablespoons of vinegar in a gallon of water. Recheck the pH after using this solution.
Camellias love soil mixtures with lots of peat, leaf mold and sand.
This will provide the acid as well as excellent drainage and aeration. Repot them every other year in late summer. Other than misting, they will only need the occasional shower to rinse any dust off the leaves. When they aren't in bloom, leaf shine can be used. Prune in spring to control the size.