How do I get a pattern from an AutoCAD file?
This does not refer to customising hatch patterns, but if you have a particular hatch pattern in AutoCAD that you want to use in Revit, there is a quick way to load it. In AutoCAD, draw a rectangular polyline and fill it with the hatch pattern you want (you may need to adjust the scale of this hatch), save it and import this dwg file into Revit then explode the dwg. Now this hatch pattern can now be found in the model pattern type of your Fill Patterns in Revit.
I've found this to be helpful when I need a new hatch pattern on the fly.