In those articles they suggest POR 15, I actually did not like POR 15 because it can bubble very easily and can look crappy. I prefer Eastwood rust converter followed by eastwood rust encapsulator. Neither should be used on visible parts if at all possible. I do recommend using a weld-through coating if possible.
My biggest recommendation is when it comes to welding the panel in, I have three words: patience, patience, patience. Trying to weld quickly is most newbies downfall.
Lastly, cleanliness is next to godliness. A good weld occurs when BOTH materials are clean and aligned.
Randy