Use an artists matte varnish thinned to about 50 to 80 percent. Use only a couple of coats. Apply, let dry about 3 minute, rub off everything you can with a soft cloth. Then 'scrub' the surface with a stiff bristle brush (this gives a dull finish, which is historically correct). There should be no surface buildup. There should be no shiny areas (there were no shiny surface paints before about 1930 or so). When you see a model of an 18th century or 19th century (or earlier) ship covered in shiny varnish, you are looking at a project that was very poorly researched. A good 'vrnish' to use is 'Liquitex' Artist's Matte Varnish. You can buy it over the internet and in artists supply stores. A pint will cost about 15 bucks and last a decade or more. You use very little per model. This stuff really works. However, it behaves differently on different species of wood (hard wood, soft wood, pourous wood, etc). You need to learn it's characteristics; in general, it is great.