https://aescripts.com/pathblurfx/

Blur effect along the mask path with full control in After Effects

• PathBlurFX v1.0 (aescripts) is an After Effects plugin that lets you create a directional blur that follows a mask path. It generates a vector field from your mask, so the blur flows and curves naturally—great for motion-blur / smear / melt-like looks on footage, text, or shapes. You can control blur falloff along the path (different strength at the start vs. end), offset where the blur ramps, and smooth sharp direction changes for cleaner results. It also includes Dynamic Sampling to keep sampling density consistent, all in a simple, minimal UI.