Bartlett normally hires deconners with > 6 months of experience. Other companies follow similar guidelines.
Some utilities have their own people called services people or station persons (used to be stationmen), so they don't need decon support.
For years, it is the job that was filled by someone's other half, sibling, relative, friend or what have you. Normally, you don't prepare to start a career of decon. Alot of HP technicians came right out of the bar or the military and got handed a meter and were told to start using it. They may hand someone a mop and say start swabbing.