get an idea of how much of the area is rusted use a wire brush to knock the paint off. Cut and form the new piece of metal to the area by bending it so it sits on the area flat without rocking before you cut the rust out. Then cut the rust out test fit your piece tweek it if you need to. tack it in check it again if it's good stitch weld it in but keep the area cool so it won't warp on you I use a wet rag then clean it sand it fill it paint it and drive the bloody snot out of it. Sorry I don't have an after picture