I know you are asking about spray varnish but as spray varnish has lots of imponderables when using, I never use spray varnish, always use a paint brush “Daler Rowney Acrylic soluble matt varnish”. Always stir well using a wood coffee stirrer placing varnish on a clear tray ( I never use the last 20% at the end of the jar). Then brush minimal amounts of varnish over the figure, better two thin coats than one thick. Taking care that there is no build up of large amounts of varnish. This method is time consuming compared with using spray varnish but it negates all the problems and I get good results.
The left over 20% at the end of the jar is used for varnishing bases where any whiteness is hidden by flock or paint.