Even if it doesn't contain pore clogging ingredients, clients should NOT use liquid foundation.  These are very aggravating to the skin and can contribute to breakouts and inflammation.  

Priia Liquid Mineral Foundation is the only exception for acne safe liquid make-up.  It is streaky and lots of clients do not like it.  You can suggest wetting a blender ball, and tap it into the skin to help with streakiness. 

Priia sells samples on their website so clients can try it before spending a lot of money on something that may not work for them.