Aussiedistiller, Home Distilling, Moonshine, Home Brew

Today I was gifted 2 barrels!
A 5 gallon (~20 liter) and a 15 gallon (~75liter). Both filled only once and dumped this week by a local small distillery.
I make bourbon / whiskey and have only ~4 gallons (~16liters) of UJSSM at 65% ready for a barrel.
My fermenter is a 30 gallon (~120 liter) poly drum and I currently have an 18 gallon (~72 liter) Angel yeast yellow batch fermenting....10 days now.
I have another 800 grams of Angel and all the grains to go with it and fully stocked feed stores within a few miles.
I have other fermenters and yeasts to use as well.

So you say 'that's not so bad'....but there's a problem which I hope I can overcome. Possibly a BIG problem!

The 5 gallon barrel is a barrel of unknown brand and it WAS FILLED WITH AGAVE.
The 15 gallon barrel is a Barrel Mill brand barrel and it WAS FILLED WITH BITTERS.

How can I "rinse" or clean or "condition" these barrels for whiskey? ......can I?

The agave barrel may not be so bad but the bitters barrel is pretty powerful.

Could I rinse-rinse-rinse-rinse then bung them and put in the 16l of UJSSM then roll them around them for a while?

How about a hot backset soak?

How about some trub from a whiskey ferment from my Angel yeast yellow? ... What would the koji / rhizopus / oryzae do to the barrel?

Any Ideas guys?


-Hormesis-

.....too late for edit on my above post....

How about partial fill with pea size gravel and water for a slurry then roll it around?
That would probably remove most if not all of the char but I'm brainstorming here guys.

Slurry of activated carbon or home made charcoal?

Ideas?

Put rum in agave barrel and neutral in bitters barrel.
Probablly not doable since you make whiskey.

No idea how you would get rid bitters other then with neutral.
Agave may not be terrible in whiskey.

You will never get rid of the flavour in the oak even with a shave and char.

Like Bluc said I would age something in it that you think would go well with the existing flavor