The vacume system I described will let you collect a boat load of WMO out of someones oil collection tank quickly with little mess and then let you pump it off your truck to your filter barrels without breaking your back trying to wrestle 55 gal barrels full of slick used oil... [ever try to hug a 55 gal barrel with a "little spill oil" on the sides?]
Your grain transfer system might work, but I'd want to give it a try first...
When you draw a vacume of 10/20 psi on a 55 gallon barrel you might be in for some suprises...
I know my vacume system works with WVO or WMO.. cold or hot... thick or thin...and it moves a 55 gallon barrel of oil in about 15 minutes.
Did u get that right? 15 mins to pump? 55 gallons on a super sucker should take about 1-2 minutes tops to fill at collection.