John comes off as being quick tempered, with a short fuse, and obviously of military background. When he was growing up, he probably endured corporal punishment up until he moved out of the house. And given the time when the boys were raised, spankings were still common in America. I think John would have spanked the boys up until they turned 13. Reason 1: extra PT would do no good to a chubby 8 year old Sam or a 10 year old Dean. It just would not be practical or effective, since the boys wouldn't comprehend the meaning behind it. As much as the boys had to grow up fast, children are still children until a certain age. Reason 2: quick and effective, spankings would get John's wanted results, a behaved child, although probably a sad and angry one. Reason 3: Grounding the boys seems silly, since they probably wouldn't have gone out in the first place, there would be nowhere to ground them from. As well with taking privileges away, what do the boys have? Probably very little having to move around so much. Reason 4: The Winchester Men seem highly unlikely to care much about cleanliness and such. I don't see John giving them chores to do, so extra chores wouldn't make sense. Reason 3 and 4 work well with older children, but would be replaced with PT in the Winchester house.
For as much as John comes off as a horrible father, I don't think he would ever hit the boys out of anger, or if that were to ever happen, it would have be once and he felt like scum afterwards. I see him spanking the boys when they deserved it then leaving the room and having the boys pull themselves together. Then the boys would be the ones to seek forgiveness or acceptance from John again. To me, John seems to be rather reasonable and fair in a very odd sense. His love for his boys makes him so; if he were ever so angry at the boys, he would walk away and then deal with the situation.
Overall, I think John would spank the boys for talking back, being too loud, giving tantrums, etc. when they were children. John would give more threats than anything as the boys grew into teenagers, a good "you talk like that to me again and I'll kick your ass" and the boys would straighten up immediately, knowing John didn't just talk. He definitely walked the walk. :) As the boys became teenagers, it would be harder to physically control them with spankings, and PT would be more effective, like the equivalent to groundings. But, as we saw in "Dead Man's Blood", John's not totally striped on the physical contact. He has the short fuse, easy tempered, so I'm sure he shook the boys as teens, slapped them in the back of the head, and if they did anything that deemed bad enough, I wouldn't put it past to him to give them a dose of his belt. But mostly, I see threats working with the boys as teenagers, as corporal punishment at 17 is quite humiliating and embarrassing.
I totally agree that John would give extra PT and "chores" to the boys; but, only as teenagers. He may have used time outs occasionally with them as kids, but most likely wanted a fast solution found in spankings. I can see John having a sailors mouth, but not wanting his boy's to be disrespectful. So, in that John would threaten or actually wash the boys mouth out. And someone mentioned sending the boys to bed without dinner, I can see John doing that as well.
I think we also have to look at who the boys were left with when dad was away. It seems widely accepted that the boys would stay with Paster Jim for few weeks here and there, as well as Bobby. I've seen Pastor Jim reflected two ways in fiction; one, taking the boys under his wing and babying them in comparison to John. Or two, just being an extended arm of John, but with his own twist. I would think Pastor Jim, would be more the second, not being afraid to spank the boys... he is a pastor and I don't mean that in a gross way. The same with Bobby. Neither would let the boys walk all over them. So, if John never hit the boys, if they were ever left with Pastor Jim or Bobby I bet they were.
Given the circumstances and timeline, I think it's impossible to think John was reading parenting books on alternatives to spanking. About how often he spanked them, that's for the the imaginary I guess. How "bad" do you imagine the boys being? I can see Dean taking the blame for a lot of things Sam may have done and thus being punished in his place. But Sam being a mischievous, rambunctious boy, he probably got into enough trouble to get himself spanked. Some fictions have put it in the light that Dean would never want his baby brother to be hurt. I agree with that, stepping in to take the punishment or begging his dad not to spank Sam, but again, only up until a certain age. Eventually Dean's not always going to want to take the blame of Sam in this sense.
So, that's so long and hopefully not to confusing, but if it is, just ask and I'll explain more.. In general, I can see John spanking the boys whenever he saw fit and using extra training when they got older. But always holding it above their heads that he could kick their butts if he wanted to. But spanking a teenager will probably lead to more rebellion than anything, and John's smart enough to realize that... Well hope this helps you!! I just seriously cannot imagine John NOT spanking.
real post next :)