I use the Obagi 6-part system for hyper pigmentation. If I add this to my regimen, at what point should I apply it?

Hello, I am actually an Esthetician and my medical spa sells the Obagi products. If it's at night, this should be the last thing you apply. If it's during the day, it should be the last thing you apply right before the sunblock. Let everything soak in before applying sunblock. If your skin is not very dry, you might only need to apply it at night but if it is more on the dry side then once in the morning and once at night should be good enough.

Is this the authentic product? My derm's office sells it for 49.50, and the Obagi website warns against buying from several sites as counterfeit.

I can't say whether this is a knock-off or not but I've used this product as part of the 6-part Obagi system and haven't noticed any difference between the one I initially purchased from my derm and this product. What I can say is that the online retailer (not Amazon) that I use for the other Obagi products offers substantial discounts in pricing (although not as low as this price) whereas my derm does not. I've used Obagi (purchased from the online retailer after the initial purchase from my derm) and gotten the desired results. My derm cautioned that the expiration date (there isn't one on this product) on Obagi products purchased via online may be substantially shorter than the expiration dates on the products he sells, so that can be a factor to be aware of.

Can makeup go on after using this?

Yes, you sure can. But don't forget to wear a sunscreen before your makeup.

Q about nu-derm system: after cleaning with 1 and 2, applying 3 and 4 then moisturiser and sun shield seem too many layers on the skin. is this right?

I apply many of the same products: C&E serum (applied on damp skin and absorbed), then Obaji moisturerizer, sunscreen & skin repair mixed together and applied. Foundation and makeup goes on last. All keep my skin protected and hydrated all day albeit a little greasy, initially.