G'day again SJ,

You wrote:

......but over an acre or so its too big a job to ever finish.....

Lucky You!...You make us jealous with your 'acre or so', but
anyway, with that much space you may already have chooks, and they are a
good way of pecking out old seeds and bugs from any area of lawn, and eat
new weed seedlings as they emerge.

China
Wingham
NSW