Yes, watching paint dry / watching grass grow means that an activity is very, very, boring. This is certainly understood by all native English speakers, because it is used once a while (but not every single week).
English is not nearly as colorful or vivid of a language as Chinese, when it comes to idioms or how much information you can compress into few words (Chinese can compress a ton of information into just 3-4 words but English cannot do that). In any case, other English words that describe really boring are: "tedious", "mind-numbing", or even better, using these two together: "mind-numbingly tedious"