There are many ways you can increase the resistance of your pull-ups. You can add extra weight to your body with weight vests or a dip belt. You can also progress your technique as explained in Convict Conditioning.
Both of these methods are effective, but they also each have a drawback. Adding weight to your body can place more stress on your joints. You also need to have the necessary equipment which may be difficult to come by when traveling. Advancing your technique is extremely beneficial, but it takes practice and skill to get used to the advanced exercises.
This is why I enjoy using techniques that challenge your grip. By taking a finger or two off of the pull-up bar not only challenges your grammar muscles but it also makes all of the other muscles involved in a pull-up work much harder. It’s also something you can instantly do to make your exercise easier or more difficult in the middle of a set. Plus, you don’t need to learn in advance text me or use fancy equipment.
Check out this video for a couple of examples of how to apply this effective technique in your training.