Varnish, shellac, lacquer, etc., would not be expected to be suitable for coating foam bugs, as these finishes dry 'hard'; i.e., non-flexible. As a result, 'flexing' of the body ( a hit and take by a fish) with such a dried finish would be expected to result in a seriously cracked finish coat. The fabric paints would be expected to be ideal for this as they are designed to be applied to material that is constantly being flexed, and holding up.