This may be part of your problem. Flat and satin finishes have a lot of bumps, humps, nooks, and crannies. That scatters the light and gives the surface its flat or satin appearance. Gloss is smooth, and reflects light back towards the viewer, giving a shiny appearance. The surface finish also factors in regarding how liquid flows across its surface. A flat or satin finish will want to grab and hold the liquid, while a gloss finish will allow the liquid to flow smoothly.  Try using a gloss varnish. I think you'll have better results regarding the flow of the wash over the surface.