Nick, Charlie
I ordered directly from Schiffman. The easy part is telling him what you want, I got book 21, 22, and 23. Gave him my address. He sent back how much the three books would be and the shipping in Euros. He shipped them DHL. Be prepared to translate German. Whenever I deal with another country I always send English and a translation into country language as a courtesy and to make sure we communicate. They were nicely packaged. He supplies you with his IBAN - universal account number, you have one also just do not use it, it has routing and account information. He gives you his banks BIC / Swift Number which is the banks identifier, you bank has one also.
Now for the fun part.
1. You could send him a check made out at current Euro rate, but first get his agreement as to how to calculate rate, he may have to pay a fee to cash your check.
2. You go down to your bank with the information he provided and ask to do an international wire transfer. Then depending on your bank size, ours had not done one in over five years, and discover our archaic banking system requires his address, and an address for his bank. None of which is relevant since it is in the IBAN and BIC. Next they will want his account number and they do not know how to decode the IBAN (which may be different for every country). Just google German IBAN and you will be able to decode for your bank. So now you have the form filled out. Oh I forgot about the $70 fee from your bank. It gets better. You are going to pay in Euros so there is an intermediate bank that takes your dollars and converts it to Euros, if you pay in dollars still same a fee, ours was around $30. Now that everything is covered it takes very little time to transfer the money.
3. Did some investigating if there was an on-line system that was less expensive. Yes there was, I think no fee at all or very small around $10 or so. I do not remember what it was. I am sure you can find it with a little digging.
Maybe Skeptic49 can tell a story also.
Best of Luck
Gen