We assign someone other than the assembler to test each joint after assembly - because it's easy to miss something. Testing should include visual checks, torque checks (except for Belleville washers), and resistance measurements. Belleville washers are usually at the correct torque, if tightened just until they look flat. After joints pass the testing, we protect them with insulating boots. These should encapsulate the entire array of bolt heads and nuts, since bolts often come very close to other bolts in opposite phases or to the bus duct case