I've done detax at both amsterdam and paris. i think both are quite efficient but i've always arrived at least 3 hours before departure.
i usually go to the custom desk to get my goods inspected and stamped. with high ticket luxury goods, it is my experience that they will always look at one or two pieces. thus, i always make sure that they r packed with easy access in my luggage should i need to retrieve them. after i get the custom stamps, i would simply take off my receipts and mail the form in the accompanying envelopes. there is always a mailbox nearby so it shouldn't take too long to do this step. then i check in my luggages (but not my Hermes bag, of course!)
i didn't realize that you can get Hermes refund through Global Refund (nor do I want to) since Hermes processes their own tax refund. however, on some of my Global Refund form, i have read that if your store happens to use Global Refund as their processor (I think
Prada and BV use them), you can get a credit card refund right on the spot, provided you go to a Global Refund desk. That way, you don't need to wait the 5-8 weeks nor do you need to pay service charge for them to give you cash. In Hermes case, as the amount is quite high, I'd prefer my credit card to get the refund as well as the overseas charge that they charge us (up to 3%).
oh, Hermes only refund 10% because they want to make money on the refund as well and you don't get tax refund on the sale items as well. with other luxury goods, i typically get about 13%.