I'd DOH all the warmup sets to get the grip work.
You might have to alter this slightly if you find that too many warmup sets may be affecting your ability to use a good strong hook grip. If your hook grip starts to fail on later sets, it may be because you did too many DOH warmup sets. In that case, either switch to hook grip a bit earlier in the training session, or use longer rest periods between sets.
I'd certainly still use chalk with or without a hook grip.