Varnishes

which would be the best to put on an olive drab tank, matt, satin, or glossy, or that future floor wax

Manik - with armoured vehicles the end result should always be a matt finish. But decals do not adhere well to matt finishes so what a lot of us do is apply future first, apply our decals, then apply a matt finish such as Testor’s Dullcote.