Yes and Yes ! Layering SPF rich products is a double-check that you are applying a sufficient amount to protect and cover all your bases. Sun protections is paramount 365 days a year. It will protect fragile skin from aging, wrinkles, discoloration and most importantly skin cancer. A SPF of 30 or greater is necessary, must be applied last and must be lathered on. What genre of sunscreen you choose is your choice: sunscreen targeted for the beach, an anti-aging sunscreen, a moisturizing sunscreen, a foundation with a SPF etc. Just follow the guidelines of choosing one with a minimum SPF of 30 and apply enough of it, don't be stingy.
Layering sunscreens is surprisingly facile, there are no steadfast rules. Dozens of studies show that whatever you can do to get more sunscreen on will mean you are better protected. FDA guidelines state that most do not apply enough product and most do not re-apply every 2 hours. The only hiccup is how much more protection you get from layering is not clear. Applying a primer with a SPF of 30, then applying a moisturizer sunscreen with a 45, followed by a foundation with 15 does not equal a SPF of 90, but it does equate to more sun protection. Sun damage will begin the very 1st minute you walk outside, application needs to be 20 minutes to all of your parts and pieces prior to exposure.
What does a liberal application mean? Smooth on a visible layer, massage it in and if planning say a beach day, spread on another layer. Sunscreens break down via direct exposure to the sun and therefore have to be re-applied. And UVA rays of daylight are every: through car and office windows, even if just running to the car.
What about applying makeup over sunscreen ? Love layering. Allow sunscreen to set prior to applying makeup, use light pressure and better yet find a makeup base with sunscreen. Not convinced that sunscreen must be an integral part of your daily routine, according to the John Wayne Cancer Foundation "skin cancer is the most common cancer in the US with 3.6 million people diagnosed annually, and its on the rise. 1 in 3 Californians will be diagnosed with skin cancer during their lifetime. 95-100 % of skin cancer is curable if caught early and treated quickly. So Block the blaze.