At Maitri Fitness we recommend using liquid grip aids, such as Dry Hands or Tite Grip, when pole dancing, for weights sessions and for yoga, if you find your hands and feet get sweaty enough to affect your gripping ability.
When you apply your grip is very important to make sure that it works properly, and most people aren't aware of this.
The best time to put on your grip is before you even start to warm up. It is an antiperspirant, just like what you put under your arms. If you're already a bit hot and sweaty then your antiperspirant can't reverse that effect.
What's best is to put it on your hands, feet and anywhere else you need to be be able to grip, about 30 mins prior to exercise. This isn't always possible, so just as early as you can is best.