I know that this may be obvious to most already using OpenGL, but I'm still fairly new to it so that said...

How do I ADD, SUB and MUL a texture to the screen? A simple alpha isn't really what I'm going for as I'm trying to create an explosive effect that will brighten the colors as they are combined on the screen.

I'm almost sure it's the glBlendFunc(); function... but what are the settings I want?