Originally Posted by Polliwog
I'd redirect him to a place he can spit. And remember to phrase things positively. The brain has a harder time translating what not to do into what TO DO.
It is certainly harder to get rid of a behavior than is its to substitute a alternative behavior. I neglected that in recommending just ways to mildly punish or extinguish the spitting.
Acceptable spitting is similar to unacceptable spitting and it's tends to be easier to shape a small change.
But when substituting an alternative, you need to substitute a behavior with the same function.
I am assuming that the function of the unacceptable spitting is to get parental attention. (It's worth noting that that is just a theory. Everything is a experiment based on hunches geared at finally finding something that works. I think the most important rule is the "2 week rule" that if you don't see improvement in 2 weeks then try something different.)
So, to successfully substitute acceptable spitting, you will need to give it attention. And, if you keep having to redirect unacceptable spitting, it's still kind of gross to have the kid spit on you initially.
Also, the root cause is probably that the baby is getting attention that the DS use to get. With the new baby, it's harder to give DS all the attention he wants.
Because of all this, I would try substituting something like acts of kindness or helpfulness directed towards the baby. That way, attention to DS is synergistic with attention to the needs of the baby.
And, you can do both redirection and encouraging kindness with attention.