I have only used material effectors in projects becaus e unfortunately they effect all models they hit
here is a quick sample how I think it can be done based on a decal or decals here I used a material for the landscape (very basic) applied a decal that started out as color percent 0 % had the explosion sprite material for a few frames then turned up the color percent on the decal which had an alpha channel to alllow the not effected area show through. I believe two decals could be used with the color % changing the same way
bacon.mov