As usual, I've written a novel instead of a couple lines. Deal with it. :D

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Not so much a father/son relationship here--I've got no kids--but at work I am often called upon to work with new hires or given helpers who don't know anything about the job they're helping with. In both cases I want the helpers to learn as it is likely the job will need doing again. Whether they will then tackle the job themselves, or assist me again, I want them to remember enough to make it easier than the first time.

I try to break the job up into parallel tasks. That is, if doing a brake job and an oil change, and the new worker has some clue and a shop manual, I take the oil change and assist with the brake job.

It's important to have a "job of your own" to save you from leaping in and annoying your charge. He/She will have their mind full (hopefully) with the task at hand, and judging when to say something and when to just keep away is a tightrope. Being right there, but occupied, allows you to look up and say, "hey, how's it going?" without looking like your eyes are in their workspace the whole time (although, we know, they are...). You're also in earshot for when they ask for a hand, and able to see that they forgot the little clip that goes in between those two other parts and they'd have to tear it all apart, or the wheel would fall off, or...

So when that moment comes, I always then pretend I've reached a break point. I pop up and say, "hey, I was just gonna go grab a cup of coffee, you want one? Oh, and I can look up the torque spec for that manifold while my hands are clean..." or, "Let's grab a snack and when you get back I'll hold that brake cable while you get the parking clip in place..."

That way it's not me being pushy or taking over, I'm giving my advice while I'm pretending to just help. It gives the new guy a chance to pretend they knew it all along, and gives me a chance to see if they just forgot, or if they're a complete idiot, or if they have a way of doing the job that I don't know yet (and if that way is any good...).

I save the humor/trash talk for when we have the actual breaks, and I try to make sure that for every comment on the worker and job at hand, I tell them about one of my screw-ups (very many over the years...and I'm only 36!). I've found if you badmouth someone or their work mid-job, or in front of people, they remember that much more than the job they've done. Save it for when they've got a soda and snack and their mind has gotten off the job a little.