I also punish him other ways in addition to spanking him (but spanking is the main thing). One that I use quite a bit is making him wear women's panties to get it. This is pretty effective at embarrassing him when I make him put them on. I have two different pairs he has to wear, one is a pair of my old white cotton Hanes Her Way panties and the other is a pair of pink rayon panties. I let him change in privacy because I will make him wear them all day long before or after the spanking, even to work. I tell him he is going to have to sit down to pee today.
When I spank him I always spank him on the panties first. While I'm hitting him with the hairbrush over my lap, I tell him he's a bad little girl which I know makes him embarrassed too. He was wearing the white pair the time that SH spanked him, and she told me she had asked him before she started if it embarrassed him. He said it did. One time I was spanking him while he was wearing my panties and he tried to resist. I grabbed his hand and told him that I would punish him with a tampon if he didn't behave. You know he behaved instantly after that.