Not getting your point.

I put all the items that I want to purchase into the basket.
I apply (if available) a coupon code.
I remember the final value in the basket. OK, the paper, where I write the value on, will remember...
Now I move all items from the basket into the wishlist, so they are still easy available. Pro tip: Click on the small arrow close to "remove".
Then I buy a gift certificate for the value, which is recorded on the piece of paper.
Within a few seconds the GC will be available.
From the wishlist I put all items back into the basket and pay via GC.

No GC balance left and PP f...ed.