Use a relay. That Instructable seems better than most others.That kind of power supply will have a very high inrush current when it's switched on. Make sure whatever relay you buy has a lot more amps than the power supply does.
How I know the inrush corrent?
After all that will not be a power supply, will be a transformer because will be ac to ac
Better ones have a NTC thermistor to limit this, but they tend to have a significant failure rate.