textures/transit/jher_flood_d_blood1
{
surfaceparm noimpact
surfaceparm nonsolid
surfaceparm trans
polygonoffset
{
map textures/transit/jher_flood_d_blood1.jpg
blendfunc filter
}
}
noimpact means entities don't hit it
nonsolid means entities can pass through it
trans makes it so it doesn't affect the VIS
polygonoffset sets it a predetermined distance from it's plane (lifting it off the underlying texture)
blendfunc filter removes the white pixels in the image iirc
Simply analysing the included shaders can teach you a lot. Try it out.
By this you can see that if you simply replace the dirs and images and have that which needs to dissappear be white and you're all set.