Blit a material only on the layer rendered by the camera ?

Hi !

I have 2 cameras on my player, one is rendering everything except the arms of the player, the second renders only the arms of the player.

I use a blit operation on my cam to give a blur image effect. But the problem is that the blit operation is executed twice. (because the 2 cams have the same renderer).

Is there a way I can blit only the masked render texture of my camera layers ? In this case, I only want to blit the arms of the player.

Thank you