Instead of hosing down your drkrm in large quantities of dektol I'd strongly advise you follow Magnus' advice - use troughs and scroll. Not only does this technique save you from having to mix huge amounts of chemistry (one gallon of working solution should be enough for two 30x40's) and fits in your sink (my troughs are 48"long x 12"wide x 3"deep), it's also the best way to get uniform development and archival washes. Furthermore, the cylinder of the scroll is a lot more rigid in fluid than a giant, flat piece of paper and so A LOT less prone to crimping and other material handling problems. It may seem counter-intuitive to your standard process w/ trays and tongs but having done hundreds of murals this way I can't imagine a more simple process. BTW, a couple 40x50 sheets of homosote and some push pins works well for viewing and drying. Good Luck!