How long does the process from start to finish usually last?

It depends on a few things:

The time it takes for athletes to search and apply to your campaigns.
- You can speed this up by sending invites to athletes to let them know you're interested.
The time it takes for you to accept athlete applications and send out proposals.
- How to view your applications.
- How to send a proposal from an application.
For product deals, the time it takes for the product to be delivered.
- Recommendations for sending out product deals.
Finally, the time it takes for athletes to complete their deliverables.
- Best practices for getting what you want out of deliverables.

You can make this as easy as possible by being incredibly specific in your campaigns, proposals, and applications as well as agreeing upon a time-frame for deliverables.