With xgen you can generate guides from groomed hair that you can then use to place custom geometry. xgen groomed splines are essentially just bent cards with auto UVs anyway. The main problem with using them is a lack of precise control over orientation.
You can convert back and forth between groomed hair and the other stuff in xgen. It's in the documentation but you'll have to dig a bit to find the best method
Grooming I'm not sure as I haven't tried, but I found this and thought it was possible: 'XGen Arbitrary Primitive Generator is the system used for hair in both Disneys Zootopia and Pixars Toy Story 3'
Is there a way to Comb a custom mesh in maya or zbrush? Like combing fibers in zbrush or like xgen-hair? I know i can create a InsertBrush in zbrush, but what do i do than to make this groomable? :/