Nah Co2 is too spattery buy 5% mix and you'll get much cleaner weld.
Also 90% of the time where people go wrong with Mig is the wire speed is too slow and they travel too slow dumping more heat than needed into steel and giving raised welds.

Preparation is key so nice ground fillets on edges and with well setup machine then you'll run perfectly flat welds in no time. No grinding Required.