Will rust reformer work?

rust is like canser have to cut it all out. you onley see a little but runs deep . if you have a rust blister that little blister . have to take out a peace of metal the size of a teness ball . to get back to clean meatel . rust reformer to me is good when preping . fix metal as a metal prep for repair . its to late have to remove all rust an metal back to good metal an rust prep fill with plastic or fiber glass sand to fit re prep an prine an paint