In the case that you do decide to do a QHFD, it must be direct. Spouse A's IRA into spouse A's HSA, and spouse B's IRA into spouse B's HSA.
However, most of the time, you will save just as much money by doing a regular withdrawal from the IRA, and contributing that to the HSA, as you would doing a QHFD, because the tax deduction from the contribution offsets the tax from the withdrawal. The regular withdrawal has less paperwork, and can be done as many times as you want, while the QHFD can only be done once. And, once the money is in your checking account, you can contribute it anywhere you want. i.e. spouse A can withdraw from their IRA and contribute it to spouse B's HSA.
I suppose there might be a situation where you would save more taxes doing the QHFD, but I can't think of an example.
