I have used self-levelling screed in the past. If tempted to do it yourself, then you need to be very organised. You have just minutes to do it all. Don't even think about hand-mixing - power mixing is the only way to have a chance of doing it in the available time. Plan your actions carefully and rehearse them. Wearing football boots (so the studs are short "stilts") may be an idea, if you will need to traverse treated areas.