Saxon, I use the closed headed drums with the 2" and 3/4 " Bungs in the top. I simply find the center. mark it with a sharpy, then use a plum bob with Flo-orange. Make a few small pilot holes and cut in half with my Saws-All . Debur the lip and then crimp it 1/2" so as to not cut my clumsy self. Been there done that!
71GTO,
The only potting soil that I use when doing any type of above ground gardening . (planter boxes, pots , Tires and or raised beds). is Mel's mix from "Square Foot Gardening" books . its 1/3rd each Peat, Vermiculite or Perlite and Compost. The mix is lite and airy ,promotes good drainage and provides some nutrients due to the compost. I have been using the Square Ft. garden method for many a year .