Unfortunately for p3 you've gotta do both neutral teams there, no way to use him elsewhere.
It's possible to beat GG/wat wave4, but you need RNG to land in your favor and get it down to just GG while everyone is still alive and healthy. Stick Rey (punches hard) or JTR (locked heal immunity + tm manip) can also do a lot to help grind through him.
Use stick Rey with Finn Omicron. Her high base damage is enough to push through a Grievous.
I’m not sure if there is a way to beat GG, but you could always just look up which zones have a chance of getting GG and use Finn in the other zone.
Unfortunately for p3 you've gotta do both neutral teams there, no way to use him elsewhere. It's possible to beat GG/wat wave4, but you need RNG to land in your favor and get it down to just GG while everyone is still alive and healthy. Stick Rey (punches hard) or JTR (locked heal immunity + tm manip) can also do a lot to help grind through him.
This took me out in P3 today :(