In case anyone was wondering about buying stuff at Yahoo Japan with proxy services:
I bought my last poster through From Japan
http://www.fromjapan.co.jp/en/It's a good site and everything went smoothly. You just have to open an account, and put a deposit that will cover your maximum bid. Then they'll let you know when they receive the item from the seller, and you can wait a while (up to a month if I recall correctly) to email them the shipping instructions to the USA, etc. In that time, you can wait to win a few more things, and then have them all shipped to you with combined shipping.
The last package only took a few days to arrive, and they email you the tracking number when it's shipped. Another big plus is the option to use their "sniper bid" tool on the website.
I just use Google Chrome to browse Yahoo Japan, as Chrome translates the pages easily. Then I copy and paste a url into the watchlist form on the From Japan website to keep it on my watchlist and bid on it there.
The rates at From Japan are not bad, and as I mentioned, overall it's an intuitive, and fairly simple process.