Well i being only 14 don\'t like the shiny surface, i think it makes it look less realistic and therefore defeats the purpose, but i also understand that you want something to seal the surface of the mini so the paint doesn\'t chip and what not.
But as to this mat varnish idea, i have no clue. If it leaves less of a shiny residue and provides the same protection I say go for it!
I think the general consensus on varnishes is: a coat or two of gloss varnish because it\'s harder and protects better, then a coat of matte varnish to kill the shine - Testor\'s DullCoat in particular seems to be the favorite, at least in the US. Seems to be more difficult ot get elsewhere.