A couple things -

First, international first class is air mail. The USPS no longer offers sea mail or other surface mail. They discontinued it 2 or 3 years ago. My packages typically arrive within 5-7 days to all overseas destinations (exceptions: some South American countries and Italy).

I am not aware of any affordable tracking options for first class international. I tell buyers that the Customs code is the tracking number just to keep them honest, and it can be used to track it through the customs process - but not through the post office's routes.

Insurance is tricky; it varies by country. Some countries allow insurance for first class, and others don't. I tried to obtain insurance for a shipment to Mexico, and it turns out they don't allow it. I have used insurance to Europe successfully and affordably on priority mail packages (4 pounds or more); I believe it included tracking. EBay is even offering its own insurance at about half the post office's price.

The official story on the green customs forms is that they must be processed at the post office since the mailing post office keeps a copy of the tear-off form for 30 days. Speedy delivery is important to me, so I have never chanced sending a green form through an ordinary mailbox. I don't want it rejected and returned to me.

The majority of my sales are under $25. I ship between 5 and 30 international packages a week. At those numbers, of course, I am looking to streamline the process as well as keep my shipping rates affordable for customers.