Don't know if this has been mentioned, but gibbs brothers is the bees knees for whiskey barrels. They make them in all sizes 1 gallon up. Tight white oak, sap clear and either toasted or charred with a good alligator char. http://www.gibbsbrothers.com/order_new/index.php
Soak 'em in water for 1 or 2 days (inside and out) till they swole up and get tight. Then put yer likker in it. If you get the charred one, when it's new/dry, put some marbles or ball bearings or such in it and shake it around good to knock off all the loose stuff and shake it out the hole before you waterin' it. Otherwise, first time or 2 you are gonna get lots of char dust/pieces.
Smaller barrel ages faster than bigger ones and and it's easy to overoak stuff if you aren't careful. That's easy nuff to fix if you got some whitedog to pour into it. For vanilla/honey/caramel notes, best proof on the wood is somewhere between 120 and 125 proof. Iffin' you are puttin it on the wood at drinkin' proof (relatively speaking...80-100 proof), you are gonna get different notes out of the wood.
Angels gonna get their share. Ain't no way around it. I wouldn't be puttin no plastic wrap, etc., around a barrel. Barrels got to breathe to pull the likker in and out of the wood. Movin' them around speeds things up too. I heard of an ole boy rigged up some kind of contraption off a tree limb using tackle and rope so that everytime the wind blowed....it rocked his barrel back and forth like a baby cradle.
Watch out for them barrels that ain't sap clear....or have paraffin wax, glue or other such things in them. Those aren't likker barrels.