...visitors who want to mug up their knowledge in the shortest possible time. [VERB PREP. noun (not pronoun)]

想在尽可能短的时间内突击学习知识的参观者

It is advisable to mug up on your Spanish, too, as few locals speak English. [V P on n]

你最好能突击提高一下你的西班牙语，因为当地没多少人讲英语。