From Urban Decay’s website:
“Banish greasy spots and take control of oil! Our lightweight gel keeps you matte all day long. Dab it on for touch-ups without messing your makeup.
It’s time to take control of your oil and put your matte face forward. Our lightweight gel performs anywhere, anytime: dab it on all day for touch-ups without ruining your perfectly applied makeup. It’s completely color-neutral, so it works great on naked skin, under foundation, or over makeup. Formulated to help tighten pores for a youthful, shine-free finish. De-Slick even works to keep skin matte under hot studio lights and in the muggiest of heat (so you know this addicting formula provides fierce absorbing action.)”
Image from urbandecay.com
This product is my go-to face primer/mattifier for events when my clients will need to be shine-free for a long period of time, especially if I am not around to apply touchups throughout the day. As stated above, it’s a very smooth gel you apply before your makeup for an instant matte finish which will help control oil production and make your face makeup last longer. Urban Decay says you can use it to touch up your makeup through out the day but I have never used it for that purpose, I would be worried about the gel affecting the foundation but you never know!
I have had great results with this product and recommend it all the time. It may not be the cheapest but if you are having issues with makeup lasting or shine control, check this stuff out. If you have experience with this primer let me know how it works for you below in the comments!
[This was purchased and reviewed without any compensation or incentive from an individual or company.]
Derick Cich Makeup Artistry [Blog] 
Derick is a very talented and very professional Make-up Artist Extraordinaire. He recently did my daughter make-up for her senior pictures. We were stopped by so many people asking where she got her make-up done that I made sure to tell them DERICK CICH. Thanks so much for your tips on what types of products would work best for her. My daughter looked so beautiful in her pictures. I will be calling you soon.
Thank you SO much! That makes me unbelievably happy. I truly appreciate it, you guys were a joy to work with. 🙂