If I drive my truck for 30 min with just water in my system, would it be equivalent to just flushing it stationary (the proper way to flush it)? IOW, if I just drive around with a clean water refill in the coolant system instead of keeping the truck in place and then draining, would it be an okay way to flush?
It would make no difference if you are standing still or driving the vehicle. You want to ensure you have the heater wide open when you do it to ensure you are getting the old fluid from the heater core as well as the engine. Driving the vehicle around will probably allow the process to happen a little faster, as you engine will get up to operating temperature faster. The real thing you are trying to accomplish is to get the thermostat open to allow everything to circulate.