Magento 1.9 – How to Add Additional Shipping Methods

By default that isn't possible, you must, at least implement:

• A custom Shipping Method
• A custom Shipping Form for your method, to allow customer select different shipping method for each item.
• Create sales_quote_item and sales_order_item attributes to save customer method selection

Your custom shipping method must handle all that logic, you need to split all items/weights and calculate the individual/total shipping cost/price and eventually some combination too ie:

- item 1 by usps = $10.
- item 2 by usps = $10.
- item 1 and 2 by usps = $15

Your shipping method must be able to:

• Obtain the shipping cost/price from the others shipping methods (for each single or combination possible item selection)
• Save customer shipping selection to sales_quote_item
• Recalculate all that data in all further steps in checkout
• Save quote_item data to order_item
• Re-implement any other -parent- shipping method feature, like Api calls for pickup, packages generation or tracking number getters

Finally if you want to give your customers a good communication feedback, you should modify all "post place order" email and templates in order to display all that information.

IMO is a lot of work to do, and I can't figure out a real-life case in which such effort would by justified.

EDIT

I'm not totally sure, but a partial use of some dropship extension may help... I guess

I had the same problem.

Remove "Free Shipping" configuration because you don't need it (you already have "Cart Price Rules").

When your customer qualifies for free shipping it happens based on "Flat Rate" not in "Free Shipping".