Yup..all good advise..I like the 1/8 welding rod for filler idea personally..From memory I seem to rember rods being coated with something..are they available uncoated?
You should be able to get 1/8" uncoated steel rods intended for gas or TIG at a welding supply house... but you may have to buy 10 pounds. Or you might consider stopping by a welding shop and see if they'll sell you a couple pieces.