"FAT" in music is quite subjective. In my book, a FAT vocal sound is obtained through compression. A PULTEC type EQ boost in the 100Hz region will also help "FATTEN" a vocal take quite a bit. The OP was asking how to get a FAT vocal sound and nowhere was it sugested that price was an object. Didn't you advise the use of a plugin to throw at the issue a few posts back?
We could spend years going through every aspect of how to get a good vocal track. A FAT vocal track, might only need eq and compression