What kind of grass do you have. Is it still in dromancy? If you rake the "dead" grass you will expose the soil which will encourage weed growth. You should be seeding in the fall. In the spring it will compete with weeds (crabgrass) and die in the summer heat. If the grass is dead, chances are the soil has issues If they are not resolved, you should expect the grass to continue to die. What is your lawncare program (fert/mow/water)? I'm assuming you have KBG.

You keep going back and forth on what you are going to do. First you were going to aerate/overseed. Then you were going to hire a professional when you realized all of your turf was dead. You can renovate yourself easily. Just search "renovation". It's getting close to the time window to seed so you better decide and get crackin'!

In case anyone cares, I did a hard-rake with a garden rake. It left the rhizomes and stolons of the weeds I killed, but gave me good access to the soil for my new seeds. I sprinkled some compost in a really thin layer over the seeds and everything is coming up nicely.

Never, never rototill before seeding. You'll end up with a bumpy, irregular mess that never settles back flat again. Technically, seeding should be done in August. But if you remove the lawn and have dead space, you'll probably want to seed in late March or early April (when you can see ground and before you expect it to sprout) to get a lawn in for summer. Expect that you'll have to water it thorough your limited summer (it can still get pretty warm in Toronto and grasses do prefer cooler weather), and any extended dry period will damage a young lawn. Don't feed until Victoria Day (er, that's the end of May for you folks, right?), then feed it normally. It'll want something by then. While not generally recommended, watering every 3 days through the summer would be just fine if nature doesn't supply rainfall regularly. A first-season lawn is almost certainly going to require this. If you have areas that didn't do well or didn't sprout in April (you will), you can reseed in early August as summer fades and evenings start to cool down for fall. It could be a bit later than that for you as well, I'm just guessing it's a tad earlier than my date of August 15th or so. It's those evenings that aren't as summer-warm any longer and where you realize summer is coming to an end.