How do you guys handle shipping with your dropshippers?

[mustangfanatic]

Currently I mostly dropship all the items that I sell. I was wondering how everyone sets up their shipping? I kind of know the weights of each product but it is mostly just a guess. I don't know the dimension of the boxes either. Is there a more accurate way of doing this?

Also is there a way to set up individual shippers for different products? For example I have Product A that I want to ship USPS and the Product B will ship UPS. Is there a way to distinguish these between each product?