Why do you want to use acrylic inks is it for shadowing large zone ? Or something like around pockets, ropes, under upper eyes lits, or ...
Or is it for instant shadows on 25mm for wargaming ....Large zone, I use ....oils, pockets etc ... sepia India ( China à inks ) with a pen .
Wargaming , there is a special mixture from game workshop , you paint the way you like, than put the figurine in a bath of the mixture or use a large brush to rufly overcoat all with the mixture then with a sponge pass lightly on ...