Last year I purchased an extension wand for my power washer, and the kit included 2 angled heads. One is for cleaning the siding of the house, the other is for cleaning gutters. Both work very well for cleaning barrels, getting all interior surfaces in a direct spray.
Warning -- especially with the 90 degree angle head, there is a LOT of torque. Hang one tight and use both hands. The amount of force will surprise you.
Warning -- especially with the 90 degree angle head, there is a LOT of torque. Hang one tight and use both hands. The amount of force will surprise you.