Nose strips work best on a freshly cleansed face, because makeup, sunscreen and heavy creams form a layer that blocks the strip from gripping pore contents. Wash your face first, then use the strip before applying leave-on treatments. Once you peel it off and rinse, the skin is clean and receptive, so moisturizer or a leave-on serum can go on afterwards.
If your routine includes strong exfoliating or peeling treatments, do not use them on the same day as the strip. The skin is already exposed to mechanical pulling, and combining it with other aggressive steps can make the nose red and sensitive. Keep the two activities on separate days.
To make blackheads less visible over time, pair the strip with gentle daily cleansing and leave-on products that help keep pore openings clearer. This is usually more useful than relying on the strip alone. If you use a moisturizer meant for oily or combination skin, apply a light layer after the strip. If you use a serum, apply it after the strip and before the moisturizer.
For makeup, the strip can work as a quick refresh before makeup: it can make the nose look smoother and pores appear smaller for a while. Wait a few minutes after moisturizer so the skin is not slippery, then apply makeup. If you notice flaking after the strip, skip makeup on that area for a day, since makeup can look patchy on a freshly peeled nose.