Sentence:  Apply two <WSD>topcoats</WSD>, particularly to areas that are fully exposed to the weather such as the south side of the house. A total of three coats (primer and two <WSD>topcoats</WSD>) should result in an optimum thickness of 4-1/2 to 5 mils. 
Meaning of the word marked with <WSD> tags:  A layer of paint applied after the undercoat.