When I was a teen in the 70s we didn't think twice about it. Couldn't afford bike shops and there was a bike boom so it took at least a week to get anything back from the shop if you did take it in. I suspect the steel rims of the day might have been more tolerant, but it seemed to work well enough. We didn't understand dishing and we only knew of tension as a concept. If you were starting from zero you'd go hand tight and then a few turns with the wrench. To true a wheel you just tighten a little and loosen a little until it was seemed to rotate with minimal distortion using the brake pads as a guide.

I don't now advocate doing this with no real understanding of the proper manner in which to do it, but if clueless kids didn't seem to go too far afield it isn't an impossible task.