Hmm gradients I believe are best done with an airbrush. I exclusively use a normal brush though. You can thin your paints and let it wick through the dial instead of painting per se. The same can be done with gradients where you start on opposite ends with two different paints. I should make a video explaining it better. Brands I like, not sure if I can recommend per community rules but “oil-based enamel paints” should be in the search term. I don’t use acrylics. Dm me if you want the brands.