Where to Find and Catch Duskull
From Pokemon Go Wiki
Duskull are found and captured in Nest and Habitat locations.
Nests
Duskull Nests are locations that consistently spawn Duskull.
Habitats
Duskull Habitats are spawn locations where Duskull is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: