Bear spray is less effective with moutains lions for two reasons. First, they usually attack from behind, often striking with no warning. Second, they don't charge in a straight line. They're more likely to make they're way around a cloud of bear spray.
The most effective defense is avoidance: a talkative group of people with you in the wilderness bulletproof safety. Cats almost never attack people in groups of three or more.
If I ever live to defend against an initial mountain lion attack, I plan to use my trekking poles that are almost always in my hands in the wilderness.