Methods of preparing phthalonitrile coating compositions are provided, including phthalonitrile sprays, phthalonitrile pastes, and phthalonitrile composite films. In embodiments, such a method comprises, heating a phthalonitrile precursor composition comprising a bisphthalonitrile compound to a temperature and for a period of time to form a phthalonitrile prepolymer composition comprising a bisphthalonitrile prepolymer; cooling the phthalonitrile prepolymer composition to ambient temperature and pulverizing the phthalonitrile prepolymer composition to form particles; combining the particles with a liquid medium to form a phthalonitrile solution; optionally, adding an additive to the phthalonitrile solution; and mixing the phthalonitrile solution to form a phthalonitrile coating composition.