Brian, if your friend is in a rush you can do a same day application but this costs more and you'll have to arrange in advance.
Bring a couple of photographs and copies of airline tickets to the embassy.
If your friend is planning on travelling around China worthwhile applying for a double entry visa so he can leave to visit Hong Kong etc without having to apply for another visa to get back in. Small additional charge.
If friend planning on working or doing a spot of journalistic work while in China the visa application is different.
They've made some changes at the embassy recently , queues arent as big and the process is relatively straightforward. 4 weeks is plenty of time to get the visa.
If you're outside Dublin there are service who will apply on your behalf (you dont have to go there in person yourself but someone does -they dont accept applications in the post) ... for a fee!