Advice for a new lawn

Hi all, hoping to get some advice on how to nuke my current lawn and prepare for seeding with Chewings Fescue.

I'm in Victoria, Australia (ignore Northern US flair, we are in a cool season region) near a golf course where fescue grows quite well all year round. We moved in recently on a new estate and have a fairly large back yard which is basically all weeds or the wrong grass type.

I need to do the following, but not sure what order or when:

• Level with a tiller (I have a small but handy petrol powered one)
• Kill off the existing grass / weeds with glyphosate
• Lay seeds

I'm looking to lay the seeds in early September, our spring time, so what would an ideal prep look like?

Do I till, then use glypohsate, or vice versa? And how long before I seed should I till / kill?

Thanks in advance