Testors' DullCote is another matte coat product you could use. I use that on figures and on models, as a sealer coat.
As far as using a gloss medium goes, whether you use Future or some other product, I'll second using it on figures for things that are glossy by nature, like goggle lenses. I also use it sometimes on eyes, especially in larger scales.
But I also paint 54mm figures in a traditional gloss toy soldier finish. I use Future in that process, especially as a final sealer to the colors I've applied, which are a mix of matte and gloss. For example, here is a 54mm kit figure of a Prussian grenadier fifer from the Seven Years War, which I painted with matte acrylics, and then sealed with Future for a gloss finish:
I have also started using Future to make glazes, by mixing a drop of Future, a drop of water, and a touch of color. I use this to pick out the molded details of the castings. Here is a group of civilians circa 1910, from my collection of the Kaiser's Army. I used the glazing technique on these:
Best regards,
Brad