This will help you to hire an expert an hourly base, like if you want to hire an expert two to Three hours in a week or daily basis.
This will help you to hire an expert according to milestones, like according your work documentation/ modules. By adopting this method you can review your completed work step by step and make a payment of that particular completed work then move ahead to the next module.
This will help you in small projects like such projects which can be completed in two to three days or maximum in a week. You can negotiate with expert and decided a fixed price which is mandatory for you to pay that amount on completion.