Even after the lens appears dry the curing process is still ongoing. The grease from you finger may leave a mark.
Give the coating some time to dry. The drying time depends on weather conditions. One hour is sufficient on a hot summer day.
While the coating is wet it acts like a glue, dust and debris may get stuck to it.
Another precaution to allow the coating infusion with the plastic (curing) to be fully done before exposure to other chemicals.