It's not that hard to do it with battery and tray installed. Even without jacking up the car, all but the top 2 or 3 bolts can easily be reached just by laying down and sticking your arm up from underneath, though this would be tougher (impossible?) to do with SVT ground effects. Using a small 1/4 inch drive also helps.
Probably this doesn't need saying, but for spray tac's it's always easier to spray the gasket rather than the part to limit getting it all over everything.
