So yes it can be a stressful time weaning baby.
One product that I have used myself, for a fussy baby, is the Chu Chu teat. It works the same as a mother's nipple, baby has to work to get the milk out. With my son, he rejected a lot of other teats but took to this one straight away.
You dont need to purchase special bottles, you can use all the narrow-neck bottles that you already have and the teat will fit. And there is only one teat size, so you dont need to upgrade as your child gets older.
Its not a bad price to give it a try. You can order them from our webstore: http://www.breastmates.co.nz/chu_chu_teats.html