do you mean 2 child meshes or 2 separate files, when using vetex alpha you need the extra geometry either as an extra surface or as a separate mesh. The underlying layer cannot be alpha blended and must use just the 2 flag.
addmesh should add a separate surface but when painting it (or if trying to read write from b3d) you need to set the surfaces brushFX to:
layer0:1+2
layer1:1+2+32
layer2:1+2+32
layer3:1+2+32
my ted prog uses internally multisurface meshes but xports both methods, and i seem to remeber when writing to a b3d you need to reverse their order in the file.
addmesh should add a separate surface but when painting it (or if trying to read write from b3d) you need to set the surfaces brushFX to:
layer0:1+2
layer1:1+2+32
layer2:1+2+32
layer3:1+2+32
my ted prog uses internally multisurface meshes but xports both methods, and i seem to remeber when writing to a b3d you need to reverse their order in the file.