Answer: What you've read is true - soil that is bone dry will be difficult to rototill; soil that is moist will be easy to rototill. However, turning on a sprinkler to wet the soil isn't going to wet it very deeply. I'd wait until after a few days of soaking rains to get out the tiller. There's something about natural rainfall that seems to get everything equally moist.... There in Seattle you shouldn't have to wait too long before you get rain.
Although the area is reasonably large, hand raking is the best way to remove the dead plant debris and stones your tiller brings to the surface. Anything mechanical will leave some debris behind so I think it would be just as easy to rake everything into small piles from the onset.
Your idea with the Round-Up won't be nearly as effective as waiting until the fall months to eradicate the bindweed. While it's true that continually cutting the vines down to ground level will eventually starve out the roots, I think that a properly timed application of Round-Up will be just as effective. In the fall plants tend to speed up the process of transporting the sun's energy from the foliage down to the roots for storage over the winter months. This ensures the plant has ample stored energy to begin growing in the spring. Applying Round-Up in the early fall will guarantee that the herbicide will be translocated to the roots of the plant and should kill the roots when they are most vulnerable. Repeat applications may be necessary - read and follow the label directions.
Best wishes with your landscape renovation!
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