Got 2 Allagash Curieux Barrels, notice an odd smell in 1.

Hey HBT's

I live in Maine fairly close to Allagash's brewery so I was able to procure 2 Curieux barrels. My plan is to age a flanders red in one, and possibly an Oud Bruin in the other.

I popped the bung (snicker) on one of them and although there is still a scent of Jim Beam, i'm getting a much stronger smell of green apples. I'm assuming acetaldehyde is causing the smell (it is NOT vinegar smell), but there is no beer left in the barrels currently, so is this just because they had beer soaked into the walls of the barrel and its all oxidized now? I was told the barrels were dumped about 10 days ago.

Will a good rinse / star san get rid of the smell?
Yes, I'll be souring beer in these in the long run, but I do want to start with the barrels in the right condition.

As there was already a beer in there for 8 weeks, is it safe to burn a sulfur wick now if need be?

Thanks in advance for any advice!
~Row