For improving knife painting, you will have to learn the basics of painting at first. After practicing on canvas and different surfaces, you will be able to draw basic paintings but if you want to become a professional in this field, you will have to practice a lot. For becoming an expert in knife painting, you should know what kind of knives with what shape will be suitable for what kind of surfaces. For this, you will have to get some coaching classes of an expert in this field. When you will be done learning, you will have to use your own inner skill to draw unique styles in painting.
To become an expert, you will have to improve the use of different tools in a painting like brushes, rollers and different kinds of knives with different sizes and shapes. After the completion of learning, the biggest challenge is to improve your knife painting skills by using different means, you can search it on the internet, you can watch various videos that enable you to make unique and beautiful paintings.