Thanks again for your tips guys. 
I was already doing what you, Paul, suggested, I was just hoping in something faster. For instance if on a mono track in ProTools I add a “mono to stereo plug” PT changes automatically the track from mono to stereo after that plugin, keeping mono what was in mono before in the chain, which is really fast.
Adam, I didn’t know about that possibility, I think it’s gonna work faster for me. Do I just need to drag the event over a stereo track?