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For those shots where good control over the ND graduation is needed, I often just stop down, maybe throw on a ND1000 filter if the sun is already out, and use a black sock or dishtowel as an controllable ND filter, shooting long exposure or bulb mode and selectively exposing the different parts of the image by moving the towel. This gives me a lot more freedom than just rotation and translation as I can create curved shapes, vignette on all sides, or whatever other effect I want to do.
And for the situations where I want to be lazy, don't have my tripod, or have moving subjects and can't shoot long exposure, I use Cokin graduated ND filters, which similar to Lee filters in that use a square holder so you can adjust the horizon, but much cheaper than Lee. They have a bit of colour cast but with the typical wild colours of sunrise and sunset and magic hour I find a little cast really doesn't matter.