There are no real "easy" rules unless you want to take your piece to a place that does light sandblasting, but that's a bit extreme.
Still, if you use the methods already suggested, do the process outside. That will lessen the mess. Cast iron needs to be free of rust and cleaned properly to be ready to season. Don't let it put you off. You will be handsomely rewarded. A well-seasoned piece of cast iron is a piece of heaven. Far better than any of technology's Teflon creations.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!