Switch to gun main for getting mastery on soul guitar it will be way faster. I did gun main for soul guitar mastery and i got all moves in less than 15 min 🙂🙂🙂
ay dude consider me as an early subscriber also, if u deal enough dmg (maybe a quarter of the bosses health) then u can just hit them with the m1 one time and let your friend do the rest, it'll still give mastery.