How exactly do I introduce a cup?

[mrsalwaysawake]

My ds is 5.5 months, BF, doesn't do bottles. We'd like him to start learning to drink from a cup, and have purchased a few different spouted ones, with removable valve thingies so they can be free-flow or otherwise.
Also, we've started weaning, and he does quite well with one 'meal' of mush off a spoon (although has lately started to 'help' get the spoon in his mouth, so less food is getting in than when we first started!)
Today I offered some formula in a cup. He was happy to chew on the spout, but that's about it. If I tipped it up, too much milk came out into his mouth for him to deal with. I tried with the valve in but he wouldn't suck, just chewed.

I guess what I'm unsure about is:
How long might it take him and me to get the hang of the free-flow cup, so I'm not pouring too much into his mouth and he's happy to drink it? Any tips?
If weaning, should I be offering water with the food? I can't see him being able to drink while he's sitting in his high chair, as he always sits forwards (it doesn't recline).

TIA

I still tilt the cup for my 9mo. When you say it flows too fast and he can't cope, was he gagging? Or just a lot of water come back out from the mouth? It's normal they don't swallow all the water I think. DD has the same tendency with food. Stuff a lot in, spit out, then put into mouth again. I think it's just part of the learning process. DD also blow bubbles into the spout, it's all fun for her.

If he doesn't drink formula well don't worry too much. DD has no bf or formula from nursery from 8.5mo ish. She doesn't take spoon either so they can't add it to her food. But you can use formula in making breakfast, sauces for lunches, baking, etc.

When you say he leans forward I think he can't sit up really well unaided yet? My DD leans to the front on the tray in her early days too. Once she can sit completely unaided on the floor shes changed her sitting completely. She is a lot straighter, sometimes lean back on the chair, will look down into her bib to pick up food she dropped on her lap. So another don't worry from me. It will get better

I'd start off offering water in the cup along with the solids. Once he gets the hang of it you could start offering some milk in the cup (I actually used different cups for milk and water).

He did gag a bit, but mostly the milk just came back out of his mouth. He doesn't do that with food though - what goes in tends to all get swallowed.
He can't quite sit unaided yet so I suppose once he masters that he'll sit up properly in the high chair.