For one or two pins, I use first class airmail, and wrap the pins just like any other LBE going domestic mail. You do need the green and white customs form. I keep a supply of these at home, so that it's all filled out when I get to the post office.
For three or more pins (or two very expensive pins), I use the global priority, small envelope flat rate for $5.00.
I wrap the pins individually in bubble wrap, slip them all into a small plastic bag (I try to use those small yellow bags I've saved from WDW or DLR), but keeping the overall shape fairly flat. The plastic bag then slides easily into the global priority envelope and is more protected. I can fit up to ten pins in this envelope. I think the global priority envelope gets better attention when it reaches Japan, because it is obviously not standard airmail. Most of Japanese trading partners report receiving their pins in three business days! Global priority also requires the customs form.
There is a large global priority flat rate envelope for $9. It's about 8.5" x 11", and would hold one of those pin maps easily. I keep a supply of the small global priority envelopes at home, so I can seal everything up and arrive at the post office ready to mail.
I haven't used insurance because of the cost.
Please ask if you want more info.
