What is the best way to apply it evenly so I don't end up with patchy neon yellow?

Even application is the main practical challenge with a vivid shade like neon yellow. Since the formula is a ready-to-use balm, you don't need to mix anything, but you do need to distribute the product well. Divide your hair into small sections with clips and apply the balm strand by strand, making sure each section is coated from root to tip or only on the areas you want to colour.

Use enough product to cover each strand visibly; thin, hurried application is the usual cause of patchiness with bright direct dyes. After applying, you can run a wide-tooth comb through each section to help spread the colour evenly. Wear gloves and protect clothing and surfaces, because neon pigments can stain if they touch fabric or skin.

Before you do a full head, test a small section underneath—especially if your hair is porous or has been previously processed. Pigment can take unevenly on such hair and may last longer than expected, so the test lets you see both the shade and how evenly it holds. Avoid contact with your eyes, and be cautious if your scalp is sensitive or if your hair has been heavily lightened.