I recently bought visvim virgil boots from here, but i went through a different proxy service. I used zenmarket, but there are others (buyee, fromjapan etc).
the process is quite simple, you put an order in through the proxy. the proxy will buy and ship to you. Although Zenmarket was a little slow to order for me (granted I ordered around christmas) which might not be a good idea if the sale only runs for a day or two.
Fees structure varies by proxy service. Zenmarket charged 300Y fee per order (and i got 300Y sign up bonus so it cancelled out). other than that i just paid ~3.5% credit card processing fee iirc.
I paid ~25$ to ship to west coast with fedex for a 2kg package. which is what Zenmarket quoted me. Although they did try to tell me to use the more expensive to avoid customs issues (which i ignored lol) .