HDRP Layered Lit and vertex paint - HELP!

I have an HDRP in which i am trying to paint vertex colors onto a terrain mesh I made in blender and it is simply not working... does polybrush not support HDRP or 2019.3.10f1? that unity documentation says simply create a layered lit shared with 4 layers and paint the textures with vertex color.

"To set the texture up using the HDRenderPipeline layered shader, you need to create a layered shader with 4 layers and apply it to the ground objects. You can then paint the ground objects using the vertex color. Vertex colors are different because layers are organised differently."

i love it tells you how to paint vertex color on the object... in an external program?? or using polybrush??

I assume polybrush is not working because it keeps adding scripts zoom overrride scripts to my mesh that i cannot remove...

Id like to use something else but.... IDK how to people do this? how do people do vertex blending inside unity. how the hell would i do it in blender, i can have prefabs in blender?? so icant design my level in blender,,, can i??

I just am so confused and there is not a lot of answers and everything I try is broken... I cant use unity terrain because i can havev caves and custom mesh shapes for my terrain... and anyway im about to have a panic attack so im done writing this...