In addition to closing the shot and powder valves, keep you hand on the caps on the top of the reservoirs. If they fall off, the contents come faster out the top than the bottom.
I bought my bushings direct from Hornady. I'd love to hear where you can get them up here. When you order powder bushings, make sure you order at LEAST one above and one below. Powder bushing charts are only intended as a starting point. You MUST use a scale to check what your machine is throwing. The charts are notorious for reading light. Probably to keep people who don't check their charge weights, from loading shells above SAAMI maximum pressures.
John