I wrap the drain bolt with plumbers tape and then use a solid rubber gasket from ACE Hardware. I tighten it until the rubber gasket just barely starts to squish out from under the bolt head.

The plumbers tape should cure any leak no matter what gasket you choose to run. I like the rubber ones since they are soft and won't cause the paint to chip off.

The plastic washers eventually yellow, dry up, and split. The rubber ones also dry out after about a year or so, but they are 10 cents each so I just buy a small bag of them and throw them in the tool box.