Hi, I've spent many weeks preparing my lawn for reseeding. For the last 3
weeks I've left it to settle. I've treated it 3 times with glycophosphate
based weed killers but today I tackled the patches of couch grass which
have been undisturbed by the weedkiller. When I forked these patches
there was a dense mass of white roots, and these roots also extend to areas
of the garden where the couch grass doesn't look to be (on the surface).

The garden is 30' x 70' and I'd like to avoid taking the roots out by
hand (my backs almost recovered from the prepping) and disturbing the
settled soil, so:

1. is there a weed killer for couch grass - I've Googled but not found
any specific brands etc.

2. am I being too particular - the grass is quite dense but only in
largish patches. not the whole lawn.

3. any other prepping advice.

Thank you,

Neil