In my experience if I try to apply it in a humid environment like the bathroom right after a shower, it takes forever to absorb and dry. Make sure your skin is thoroughly dry before trying to apply and do so in a dry room. You can also try using a small fan to blow on you while you are applying it.
The first few months can definitely feel like a roller coaster ride with breakouts and clearing. Let's make sure you are following the steps strictly. Please take the quiz and read through the biggest mistakes on this page. http://www.acne.org/regimen-help.html
Perhaps you advanced the bp too soon. If this is the case you can slow down and decrease the bp for now while you try to get the dryness under control. My best advice is to add some jojoba oil to your moisturizer each time you apply it and be very generous with the moisturizer.
We have many adult members here and hundreds if not thousands of adult customers who use the products. In fact, I think most of the success stories are adults (perhaps they are more likely to send a story than younger people though.)
The first few months can feel like a roller coaster ride with breakouts and clearing but usually by the third month most people are clearing up nicely if used as precisely. Here's the typical "what to expect" http://www.acne.org/...ed-improvements
For week one we suggest starting out slowly with the bp, so you will wash and use the moisturizer in the morning but in the evening you will use all three products (and just a small amount of the bp). This way you are easing into it and your skin will have an easier time adjusting.
My best piece of advice is to follow The Regimen strictly. It really does work best when it is followed exactly as Dan suggests. Take a moment to also read through the biggest mistakes so you will be sure and not make any of them. http://www.acne.org/...stmistakes.html
Skin darkening in the beginning is almost always due to the skin getting overly dried out. Be sure you are moisturizing generously and add some extra drops of jojoba oil to your moisturizer when you apply it. This usually helps. Please also see the blue box on this page. http://www.acne.org/faq.html#burn