Which shader specifically is the model that you don't want to glow using?
Since the problem is that it renders its final alpha into the alpha of the color buffer, would not simply disabling writing to alpha fix the issue? Off hand I don't think disabling writing the alpha would stop it being rendered with alpha, but have never tested it myself. However if you have several alpha textured models overlaying each other using this method it might cause graphical issues, so may not be a fix for all cases.
To be clear I'm talking about adding, ColorMask RGB to the shader pass, this means only RGB values are written into the colour buffer, but not alpha.