Curing has to take place in an airtight environment, otherwise it wouldnt be curing, it would just be drying. The idea of curing is to get the small amount of moisture left in the middle of the buds to diffuse out to the dry edges, over time, bringing with it the smell and flavour. If you put it in paper bags the bud will just dry out more and more until that skunky smell is completely gone, by then it will probably be too late to cure...