Abstract: A method for priming an uneven surface of a blank uses a novel "thermally expansible spray putty". This spray putty is prepared by mixing a priming paint for the blank with thermally expansible micro-capsules in amount of 0.5 to 10 weight % of the solid matter of the priming paint. The thermally expansible spray putty is preferably conditioned with an exclusive thinner to a high viscous state enabling it to be air-sprayed. Shell walls of the micro-capsules soften at a temperature below the setting temperature of a thermosetting paint to be used in finish painting of the blank. After the blank being treated by degreasing, drying and the like, the uneven surface of the blank is coated with the thermally expansible spray putty by spraying. After suitably setting the coated spray putty, it is dried by heating so as to expand the micro-capsules to obtain a substantially smooth surface of the blank.