I personally don't work with a customs broker because I don't do any importing or exporting of any goods.
But if you do import or export goods that have to go through customs the main benefit of the customs broker would be to allow them to do all the work on dealing with the customs while you process your orders or take care of the other part of the business.
A customs broker will have a vast knowledge in working with customs and getting goods to clear their authority.
A customs broker is a professional who has vast knowledge and experience in customs laws, tariffs, rules and regulations.
The customs broker works to ensure the clearance of imported or exported goods or merchandise from authority, preparation of import or export documents including computation and payment of duties, taxes and other charges accruing thereon.
If you're importing or exporting goods overseas then you should hire a customs broker to take care of the customs clearing.
It can be a real headache to deal with customs if you're not sure what you're doing and I would rather let a professional customs broker deal with that job.