There's no way we can guess what pedals he does and doesn't have. Maybe you could find out somehow and let us know?
Also, if he's in a metal band he probably won't be interested in the John Entwistle angle...
The point of a solo boost pedal is to make the volume of your solo louder than the volume of your chords. If this is something you want then there is no other way round it.
It's possible to set both guitars to the same volume and not bother with boost pedals but the risk is that the soloist...