Hi R.,
Ah, the terrible 'twos'!! Ain't it just so much fun??
#1. This behaviour is probably linked to the 'coming into their own' phase that all kids at this age go through. So don't get overly alarmed and think youv'e just got a bad kid on your hands.
At this age, in the context of learning he's separate from you as his own person, this behaviour is not abnormal. He has found something that sets him apart from you. He spits, you don't. He likes it, you don't. This phase will pass, but in the meantime you've got to deal with it.
#2. I don't think ignoring it is the answer. You may be able to just silently wipe away the spit each time, go about your business, (thereby short-circuiting all the 'fun' and the 'riling' up of mom that your son is enjoying at your expense), whereby he'll probably stop the spitting cause it's lost its 'oomph'. But you can't expect this ignoring course of action to work, as it relates to others he spits on.
#3. This may work. He gets angry cause you've told him no and he spits at you:
** Say to 'Timmy': "Things make you angry sometime and then you spit, huh Timmy?. Like when I tell you no.
I have an idea:
I'll keep your crayons (washable markers?) and paper near and I want you to show me your angry feelings on paper." He draws,(probably just lots of spiky scribblings at this age) then shows you: "Wow! Those are some really angry feelings! Timmy, these must feel really bad. I might spit too if I felt this bad."
He probably won't still spit on you after this, since you've given him another avenue (of the 'dry' kind) for expression of anger. But if he does, say: "It looks like you're still pretty angry Tim. But spit has VERY BAD stuff in it called 'germs' that can make Mommy and other people VERY SICK - let's find something we can spit at TOGETHER that won't get anybody sick."
"But first, let's get this old yucky spit washed off Mommy. I'll get the soap and you get the towel." (Don't force this part though, if he won't participate in it. If he does though, say something like - "Whew!! I sure am glad you helped me not to get sick. I feel so nice and clean now!" Pat or hug him at this point.)
Now, back to the 'spitting together' business - it sounds crazy I know, but hear me out:
Go outside: "Timmy, do you want us to spit at that pile of dead leaves or on those old branches? The leaves? Okay. But let's make it even more fun! How about a contest? We'll see who can spit furthest and still hit the pile!!. The winner gets to pick which books we'll read before bed tonight, (or), the winner gets to tell Daddy and 'Michael' (his big brother) about our new game. And hey, maybe they'll wanna play too?"
#4. R., take inventory of your time spent in an undistracted, one-on-one time, with your little baby boy. Any attention is better than no attention. He just may be needing some more time and attention spent alone with good old Mom. 3 must haves of young children: eye contact, physical affection, and one-on-one, UNDISTRACTED TIME spent together.
Well, I hope this, or some part of it, has been helpful R..
Hang in there!