make sure you use this sparingly and water in well - my lawn has turned black, think its scorched it

It'll go brown if you put too much on, not black. If you had a lot of moss in your lawn, it will go black when you apply this.

spreading is important getting the right amount all over the lawn or you will end up with patches growing at different lengths and colours. Make sure you don't get to much in one place or it will kill the grass and make sure you don't get it on paths one drop of water and you will have iron marks all over.

Best to buy a "spreader" to apply it which you can pick up a cheapo one for about £15-20. As above, if it's going dark, it'll be the moss being killed off, however if you apply too much to an area it will look like it's been burnt away!
Use sparingly and keep the kids off the lawn for a few days after it's first watering.

This stuff is brilliant! our lawn doesn't grow and looked pale green. its a lovely dark green ans its gone mad since i put this stuff on!

I use this stuff, after two years still have plenty left. Spread finely, leave it for a few weeks but ensure lawn is watered (if not raining like now) and WHAM! After it takes hold my grass grows anything up to 6" a week in the summer. Not joking...