You can put just the vmts that need blending in a separate directory (with the same directory structure as before) and import those, which should be quicker.
If you let HammUEr handle it, it should all happen automatically without you needing to change anything.
Of course, if you want a single material that works for everything, both blended and non-blended materials, set up your basecolor and normal chains with a switch parameter as shown in the manual (repeating the example basecolor chain for normals too) to create something that looks like this:
