Guys,
I have the same problem.

I can't understand how I can use .vismat files.

I explain my steps and my problem:

i built a wall i downloaded a material from the site called "brick-wall_red" ( a .zip file where there are 2 .png files and 1 .vismat file.) i create a new material in sketchup meterial editor using one of these .png (one of these shows the red brick and the other grey brick and i chose the first one). so from the zipped folder i choose one.png file. i set everything in terms of scale and proportion and it is fine.the name of the new material is "brick red" right click and i linked the material in vray. now in vray editor i have "linked_brick red" now on in bump i link the other .png
8.i have the material "brick-wall_red"

i don't think it is the best way.
it is too weird.

I have read also that when you link the material in vray material editor (my step 6) then right click on the linked material, "import" and there you can put the .vismat file.
I have tried but I see everything grey.

any idea to help me??

thank you very much.

stef.