Lower radiator support piece...

So I managed to obtain a lower radiator core support that was removed by drilling out the spot welds. Nifty. Looking at how much metal overlap there is between the core support and the pieces it's welded to brought up a question. It's probably a simple one for experienced body people, so I figured I'd ask here.

What do you do to prep both of these pieces for being welded together? Just take it to bare metal, weld and then coat with something to stave off rust until you come back for finish work? I'm probably not going to be doing this any time soon, but I'd like to have a good idea of what the process is.