[Product Question] TO Niacinamide + Zinc: How much to apply & does it work for closed comedones?

Beauty Tips For Body Care
I just ordered TO Niacinamide 10% + Zinc 1%. I looked for other posts & reviews, but none said how to apply the product. Should I use a couple drops? A full dropper? Also, I have a couple random closed comedones, nothing serious, but quite annoying. Would the serum help with this? I tried acids but they don't seem to help that much.
Girls Blog 2015
Submitted by TPYogi