I thought his makeup was to hide the dark circles/bags under his eyes.
It's plausible that he did occasionally use make up to improve his appearance. He looks vain enough to do that kind of thing. What isn't plausible is that it's the explanation for the makeup being on the mask. Picture the scene. You are about to dismember a body using a circular saw when you catch a glimpse of yourself in the bathroom mirror. Oh my God you think, look at those awful dark circles under my eyes. I'd better put some makeup on them before I continue to dismember this body.
The makeup is from her face. She helped.
I don't for one minute believe the nonsense about dark circles under the eyes. He dropped SH off at CH on the morning of the 20th. I don't imagine he wanted AG asking where he'd got a bruise from. In fact it was probably SH's idea for him to use make up.