Are you talking about one of the following cases for U2:
- Using your right index finger to pull, while using your left index finger to push?
- Using your right index finger to pull, while using your left thumb to push?
- Using your right index finger to pull, and then using your right middle finger to pull?
- Using your right index finger to perform U U?
I guess you need to consider what comes after U2 to determine how it should be done...