Sorry open id be no use giving you advice on defiance. I'm another struggling.
Ds is unbelievable. He rarely does a thing I ask, we don't have any strategies that work at the minute. I'm not sure we've ever had anything that's worked really.
We do do a lot of what liv said though 'first and then'
Earlier, my big shabby chic type clock ds hung on it and it fell down and hit him on the head and then onto the floor, glass everywhere
the clock actually clonked him straight on his head (it's heavy) and he just stood laughing. I was sorting the curtains out straightening them out as incidentally he'd just been swinging off them in the window and as quick as that he'd ran passed me and caused havoc the other side of the living room.
He's ok fortunately, no damage done to him this time, but I'm genuinely starting to wonder how he's still alive with some of the stunts he's pulling 
He's been stuffing non edibles into his mouth at school again which is worrying me, I know they supervise the arse off him, but it only takes a second. It's been a plaster, a paint sponge, pieces of chalk, plastic pieces from a board game and that's just been today! He grabs anything he can get his hands on and really quick rams it in. They don't let him have small pieces but of course he's in a classroom....
They've had to have a chat with all teachers / TA's to make sure everyone is aware.
Again he's doing it for a reaction as with a lot of things he does, I just wish he'd choose less dangerous games.