If a client have oily skin, the best thing is to cover it with powder. If you don´t work with a make up artist, make sure to have powder and a brush in your bag in case you need it.
The key is not to add to much powder, as it can make the skin look lifeless and boring – but to much shine is not good either, as it can take to much focus away from your subject.
Another way to deal with shine on oily skin is to fix it in Photoshop. It´s really easy and quick!
Here´s how I do it: