I've only used WGA on fixed cells, not sections, so I can't speak from personal experience. Hopefully the 2 threads above will point you in the right direction.
1. Brain Struct Funct. 2011 Sep;216(3):159-69. doi: 10.1007/s00429-011-0304-2. Epub 2011 Mar 9. Fluorescence mapping of afferent topography in three dimensions
Stacey L Reeber1, Samrawit A Gebre, Roy V Sillitoe