The aliens were often disguised as pretty women and the protagonist goes underground to battle them but is overpowered and ends up waking up as an alien tank on another world. He manages to telepathically wake up other brains in neighbouring tanks and they use their new fighting abilities to overpower the aliens and send word back to Earth warning them of the farming operations.
It sounds very similar in plot to "A Plague Of Demons". URL: http://www.goodreads.com/book/show/1829054.Plague_of_Demons
The earliest I could find is "A Plague Of Demons" being published in 1985 and the aliens didn't use women as the recruitment method.
Edit: sjl found it was originally published in 1964 in serialized format, and first published as one complete work in May 1965 under the self titled "A Plague Of Demons".