The aggregation, arrangement and bonding together of priming complexes to form a coat on a Golgi membrane. Priming complexes associate laterally and additional coat proteins are recruited from the cytosol to the forming coat. Cargo proteins diffuse into the budding site and become trapped by their interactions with the coat. [ https://www.worldcat.org/search?q=bn%3A0716731363 http://www.ncbi.nlm.nih.gov/pubmed/10219233 ]