I am sure someone can add to my reply to make it more precise and I haven't detaxed from the border area for sometime now but here's what I did. (If you know the following already it might be useful for others..).
At the shop fill in the tax fee form they should probably have. If they say they don't have one, probably ring the Swiss customs to as how to proceed or go to/ring the closest French Marie. This has not happened to me.
I think the minimum to spend is 300CHF? before they charge duty in CH..at least it was then.
Then you go to a French border post and have them stamp the form, then you go to the Swiss customs. They take off the 20% VAT and them stamp it too and either charge VAT… for here 8% now?.. or refund you and that's it. Many of the borders here are open sporadically as there are also Customs officers circulating in cars who move around all the offices there. This applies to the French customs also. These 'Gardes-Frontieres' on both sides have the right to travel a certain amount of kms within the other country and perform spot checks. It is impossible to know when and where they are or going or will arrive, and for how long. There maybe some posts open open longer than others.
You can however be sure that Bardonnex is open 24/24h & 7/ 7. The custom offices there have also the advantage of being close to each other .
Hope this is of help.
Any other expriences out there.. to add something I've forgotten..?
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TogJay, Apr 14, 2015 @ 16:20