Sometimes finding a different way of doing things can make it easier to get compliance. Nagging won't work.
We still have to push difficult child 1 a bit, but I remember when I was a kid, a really good pimple face wash was best applied using a shaving brush. Because my dad wouldn't let me use his (and it was clogged with soap anyway) I bought my own.
You don't have to use expensive products with the shaving brush. You CAN just use soap, but whatever you use yo do need to be careful it doesn't dry out the skin too much and make it worse. A bar of Dove works well as a cleaner/'shaving soap' but I also used it with a more expensive cleanser for sensitive skin that I bought for easy child 2/difficult child 2. I used it yesterday on difficult child 1's back (not a pretty sight) to show him how easy it is (and quick). He commented that he can't reach his back; I told him I would do it for him, so would girlfriend, and a lot of blokes actually go to salons these days to get it done.
You can also make your own very cheap cleansing moisturiser for ultra-sensitive skins by actually using Sorbolene as a face wash. And yes, you can do it with a shaving brush.
It really helps get the skin really lathered up and gets as much grime as possible out of the pores. It's fast, it's different and especially appealing to pubescent boys who want ANY excuse to legitimately use shaving soap.
I wouldn't punish him for not washing, by refusing to buy the stuff; that just gives him the perfect excuse. Just go down-market until he begins to take things seriously. He's just a kid; they don't care at this stage.
And maybe talking to the doctor about medications might be a good idea. We put difficult child 1 on antibiotics for his acne.
Marg