Yes, I've had lots of defiant behaviour over the years. Because DS is the one who doesn't do defiance (beyond his todler years, it's a rare occasion he'll refuse point blank to do something), I only have experience with children older than your DS, 8+
I try to do natural consequences and not let things escalate. I'll use shoes as the example, DD2 used to do that, but it can work with otherr things too
So with shoes, it depends where you're going, but let's say school. DD2 would refuse to put her school uniform on, or her school shoes. Point blank screaming "NO, NO, NO, I WON'T!". I would simply say "okay", pick up her shoes and stick them in the car, and she would have to walk to the car and go to school in just her socks. If she still refused, then we walked into school and she stood in the playground shoeless. I'm sure some of the other parents thought I was odd because they would have shouted or something until they got compliance, but that just didn't work with DD2, if i shout, everything escalates into a full blown tantrum.
Or if we were going down the road to the newsagents, I would suggest that it will be very uncomfortable walking with no shoes, but okay then. We did walk there and back a couple of times with her shoe-less and coat-less, because I was not going to have a battle over it.
Turning it into a joke or fun thing sometimes worked (as long as I was feeling calm enough!). I do remember one time I wanted to go shopping and she refused to put her shoes on, "Oh, we're not wearing shoes today? That sounds fun! Everyone will be able to look at my amazing red socks" So I took my shoes off, gathered up my stuff and said we were going, and I think I got a couple of steps onto the path before she yelled and put her shoes on. Basically, keeping her shoes off wasn't defiance any more, because that's what I was doing. And yes, I was (that day!) completely prepared to go to the local supermarket (it's close) shoeless, because it was a much better option than a huge tantrum and I could turn it into a joke when people inevitable stared at us.
This doesn't work all the time, but have you heard of a praise sandwich? It's a once in a while thing, catch the child off guard with it. Basically, you insert your instruction/thing you want your child to do, in between two bits of praise, and because you just praised them, they don't so much notice you've also asked them to do something, and they are more likely to comply with whatever you just asked them to do.
I have to go make dinner now, i'll think of some other things I did/do for defiance and get back to you 