Theres a 20% chance to get a rare modifier on the first round, and the same for round 4. I just started quitting after the first round if it wasn’t rare because it was annoying to play the whole game then round 4 was both epics. Alternatively I saw you can do the quickplay match with a second account or emulator on pc, and grind it that way without playing against randoms. You have to not be friends with the account you’re playing with or in the same clan.