My SWCAH daughter is 4 mo. old & nursing.  At first I would express about 2oz of breast milk..mix it with the salt and draw it up in a syringe.  The lactation consultant at my hospital gave me some feeding tubes & I would connect the tube to the syringe & while she sucked on a pacifier or my husbands finger(if he was home)put the feeding tube on the side of the pacifier or my husbands finger & SLOWLY push the plunger. After the mixture was gone I would put her on to nurse for the rest of the feeding. 

Now, she will take the salt directly from the syringe without being mixed & then I nurse her right after. Hope this helps, KEEP ON NURSING!!!

Jessica