K.R.
I have used breastmilk in my 3 1/2 month old Daughter's nose since about 10 days old. She used to get stuffy all the time and breastmilk really clears it up quickly. I didn't like trying to use the bulb syringes- they seem so rough.
I expressed milk into a small cup and used a syringe or medicine dropper to put it into her nose. When I do it now, she gets mad but forces the mucus out and is breathing stuffy free later. I don't put much in- just enough that it goes into the nose.