Hi! Vertex paint sharpness depends from the vertex density on the mesh. If you use low poly mesh your vertex paint will be blurry. There are two solution. One is obvious, increase the vertex count on the painted ares. Second. Add a contrast node after your vertex color node, and set the contrast with a high value. The first one looks better but use a lot of memory, and in extreme case it will increase your loading time. You can also mix this to technic. Sorry for my english.
For anyone else who encounters this issue, please note that currently, the Blend Material M_MS_SurfaceBlend_Material provided by Quixel Bridge is not set up for use with Virtual Textures.
When working with Virtual Textures, the master material needs to be altered so that the material instances created from it can also use Virtual Textures.
To get the Material Blend working with Virtual Textures, you’ll need to create a duplicate of the Blend Material master (M_MS_SurfaceBlend_Material), rename it something like M_MS_SurfaceBlend_Mat_VT, and replace each Texture Sampler within with a VT version of the default textures that are currently in use.
Upon opening the newly created VT master material, you’ll notice there are a handful of Material Functions inside;