It's not automatic, and it's "up to" 70% at absolute maximum based on how long you've worked, how much you contributed to tax, what expenses you have, whether you're a single or dual income household, how much your income was, whether you have dependents, how many dependents, how severely impacted you are, etc. So 70% is the most extreme end, and most don't get it. My dad did because he had a non-working wife and almost a dozen kids, paying a mortgage, and suffered spinal damage. I wouldn't get that. It would probably be closer to 50%.
You can't just say fuck it at 18, get on that program and live the good life. You have to work and positively contribute to tax for years before qualifying.