The best media to spray through a finite tip, .25 or smaller, is an ink, water color or a dye because they have no pigment particle, or high transparency pigmented media that are more of candy-like tint than a color. You can get paints like Spectratex, Aquaflow, Createx, etc. through these size nozzles, but you'll likely have a notable amount of tip dry and clogging along the way. Their are friendlier acrylics for finite nozzles - paints like com-art, holbien, air-opaque, golden, etc. These colors, although substantially pigmented compared to the high transperacy media, tend to be of thinner viscosity that the foregoing multi-surface paints - so they spray a little better. However, they have limited utility on substrates other than paper, board, or canvas. In any case, you can get various media through .25 or smaller nozzles - but it requires more patience and knowledge of optimum performance pressures and paint preparations to do it with consistent success.